For the longest time, Mokuba has always been able to make friends with those whom his brother Seto dislikes very much as well as with others that he isn't aware of. While he may not be as intelligent as his brother, he does do his part in helping him run the Kaiba Corporation by his side like he has been doing since they were adopted into the Kaiba family by Gozaburo Kaiba himself. And when he's not doing that, during his downtime he enjoys listening to music that doesn't suck or matches the current mood he's in.
Since being in Tokyo, he's also landed himself a boyfriend. Yes, Mokuba is gay now and he loves being around his sexually hyperactive boyfriend, Mitsu Sanyu. Sometime last year, they had brook up briefly only to get back together later on. Mokuba has some domestic skills, considering that he knows how to cook, clean and take care of himself whenever he is left at home alone when his brother's away on business. He doesn't like the idea of taking advantage of the cooking staff just because they work for him and Seto. He is a very kind young boy who is easy to make friends with but unlike before, he does have a backbone now where he will lash out at anyone if he deems it a necessity to do so.
Mokuba letting his emotions get the best of him (depending on the situation he's in), still hasn't changed. Instead of thinking logically, he thinks irrationally, ending up making decisions that may or may not be right ones that would cause him to put himself in harms way. Which he is learning how to control, but is taking it a day at a time. He has started to lash out at his brother at the most random times. Half of the time it is over nothing but at the current moment, he just feels unexpectedly angry at him. This could be due to the fact that, Mokuba is tired of his brother running away from any problems that he has. Any problems relating to dueling or the company he can handle but personal wise, instead of dealing with it or talking about it, he would rather do the opposite like drink himself stupid or go on ungodly long business trips to other parts of Japan or to the states and barely call to check and see how he is doing.
Plus, he's tired of his brother taking his frustrations out on him for so long that he's finally starting to stand up for himself but because of this, Seto considers him a brat now. Secretly, he just wants his brother to be happy but learn how to deal with his problems the right way. He's also worried that he doesn't love him because of the simple fact that he's in a relationship with a guy and not a girl, having not made much of an effort to get to know Mitsu at all. Whether this is true or not it is currently unclear as the two have not resolved any differences they might've had before the frequently leave of absences.
Mokuba is now 5'5" (noting that he has grown much taller within the past three years) with dark blue eyes and originally long poofy black hair that always appeared to be uncombed, but since dating Mitsu and going through the whole 'cross-dressing phase', he's been keeping his hair managed by straightening it frequently and applying sheen to it so it always looks neat and shiny. His eyes are very rounded, not slanted like his brothers, rounded face, a tanned skin complexion but sometimes can appear peach occasionally and a very small build which is very common for boys Mokuba's age. Mokuba has worn a series of clothes but his main outfit he worn was usually a striped long sleeved shirt with a yellow vest, blue jeans and sneakers. Now, he wears anything from pants, to shorts, long or short sleeves and even dresses. And the whole cross dressing thing comes as no surprise to anyone. He's worn girls clothes to disguise himself for undercover purposes that involve his friends investigating strange occurrences around the city and discover the truth behind it. He’s done this once, dressing up as Princess Adina when he asked Yuugi and his friends to help him save his brother from being imprisoned in this own game contraption by The Big Five and the second time involved him tagging along with Airi and Mitsu, disguising themselves as female students at Tsukuba Academy.
Mokuba Kaiba is Seto Kaiba’s younger brother. Both he and his brother were orphaned at very young ages. Before that Seto was the first born child before Mokuba came along, Mokuba, being born after, their mother died while giving birth to him and soon after their father died in an accident when Seto was about around the age of eight years of age. They were stuck living with other relatives for awhile who originally used up their inheritance that was left for both of the boys to be well taken care of in case anything happened to their parents. Soon after, they were dropped off at an orphanage to live. Although Mokuba was insistently happy at the orphanage, Seto had always aspired greater things for both of them, looking towards a better future. But unlike Seto, Mokuba was not as bright or very intelligent, being very naïve and childlike.
Many had wanted to adopt his older brother over him but Seto swore to protect him no matter what, wanting Mokuba to be adopted with him which all interested prospective parents refused. And because of the boy’s nature, this made him a target to be picked on by older children at the orphanage. Of course, Seto immediately protected him from the other kids. To pass the time by until someone decided to adopt them, the brothers would play chess with one another, Seto, obviously winning each and every game. Though none of that matter, for Mokuba just enjoyed the time they spent with one another. After a few months at being at the orphanage, a man by the name of Gozaburo Kaiba, the head of a company know as Kaiba Corporation, arrived there just to perform a publicity stunt for the cameras. After being at the orphanage for months at a time a man by the name of Gozaburo Kaiba, the head of a company known as Kaiba Corporation only for a publicity stunt which Seto saw it as a chance to challenge him to chess and if he won he’d have to adopt him and Mokuba.
Around this time Mokuba was at the age of five and Seto ten. Seto won and now both he and Mokuba began their new lives at the Kaiba Mansion where Gozaburo lived. Sometime after that, a woman by the name of Diane Tsukino was employed as a maid around the mansion. She shared a close bond with Gozaburo’s adoptive sons as well as him. Sometimes, she’d even bring her children to work with her. Mostly to get them out of the house and all they did was explore around the mansion. Though one of them, Jasmine, basically got into it with Seto all the time, the both of them wrestling and getting on each others nerves. Mokuba, on the other hand, found this to be entertaining. Not to mention, he came to see Diane as his mother since he’d never really gotten to know his own since she didn’t giving birth to him. Eventually, Diane had a child by Gozaburo, a daughter that she’d named ‘Ruka’. She left the child in her father’s care, feeling that she would be properly cared for as well as given a proper education that she was unable to give. The woman did not stick around after she had Ruka, having erased Seto and Mokuba’s memories of her and her family with her powers until they were old enough to understand the reasons behind her actions.
And so, the child was raised in Domino City under her father’s care but she was raised as his niece so Mokuba and Seto wouldn’t get suspicious. Although Mokuba believed the child to be Gozaburo’s niece, however, Seto did not. Any chance she got, she would try to get the boys in trouble, finding it entertaining to see them both get punished for something they didn’t even do. Mokuba tried as much as possible to be nice to her but has a few times, went off on her. Diane eventually came back into the picture, the both of them regaining their memories of her and the cat was out of the bag that she was in fact Gozaburo’s daughter and not his niece. At that time, she was three years old, Seto was fourteen and Mokuba was eight. They were reunited with Diane in America at a maid and butler’s convention that Ruka’s robot maid Diana Tsukimoto (model name SDCC0001) had taken the children to, to get them out of the house for a change.
It was then, Mokuba persuaded the woman to come with them to Domino for a little while just to visit, because he missed her so much. He wasn’t angry at the fact that she’d erased his memories, in a way, understanding why she did even though he was still very much young. Things pretty much went downhill after that. Diane’s visit was a fresh change around the mansion again but unfortunately that is when the drama began. For Seto was planning on trying to overthrown Gozaburo and became the new CEO of Kaiba Corp to keep Ruka from getting it since she acts so much like her father. Ruthless and cold-hearted towards others. Mokuba was aware of this but what he didn’t know that in Gozaburo’s will, he wasn’t giving the company to his daughter but to Seto. And that there were some secret shares hidden away that apparently belonged to Diane. Both Mokuba and Diane gave their shares of the company to Seto, allowing him to take complete control. Gozaburo’s disappearance followed soon after, many believing him to be dead and having committing suicide to losing the company. A month later, Ruka and her robot maid were sent to live with Diane and her family in Tokyo, where they would be graciously provided for and not have to struggle so much. This is also where their bizarre adventures began.
He was only eleven years old when his brother not only lost his first duel to a novice game player named Yuugi Motou, but there when he abandoned him and the company to figure out the true meaning to playing the game of Duel Monsters. Because of his abandonment, he was kidnapped by Pegasus J. Crawford’s goons and imprisoned in his tower in Duelist Kingdom. These actions were to force his older brother to come out and rescue him but he manages to escape on his own, bumping into Yuugi and the gang disguised as a bandit. He’d stolen someone’s deck and star chips and challenges Yuugi to a duel when they discover that the boy is related to Seto. However he ends up being recaptured again by Kemo and later has his soul taken by Pegasus, thanks to the power of his Millennium Eye. In the end, he was reunited with is brother only for their former employees that called themselves ‘The Big Five’ to betray them to trap and try and kill his older brother in his own game creation. This prompted Mokuba to ask Yuugi and the gang for their help to save him (which is also when her first cross-dressed as a girl in order to fool his brother’s captors). Of course, they won the game, defeating the Big Five and trapping their minds within the game itself, killing them all. And for awhile, things seemed to have cooled down though for some reason, Mokuba has a tendency to be kidnapped by his brother’s enemies frequently.
But it wasn’t the case when strange occurrences began happening around Domino City. People were getting randomly harmed in their homes and on the street which made Yuugi call Jasmine Tsukino (his girlfriend at the apparent time) and the others to come down to where he lived because he kept hearing that people were randomly getting attacked by something unknown which of course, he didn’t know what it was. So, upon agreeing, Jasmine, her twin sister Usagi along with their good friends and Senshi as well, Rei Hino and Ami Mizuno, Ryoko Kajimotou (cousin of Jasmine and Usagi) went as well to be a tag along all went to Domino City. You see, everyone had met some of Yuugi’s friends that he’d made while living in Domino for so long.
Well, they met a few of them. Honda and Jonouchi weren’t around at the time when everything happened. But Anzu Mazaki, Mokuba and his brother Seto were. Jasmine worked under Seto as his secretary (despite her own hatred towards him) to earn a bit more money to put through the house so they could be able to afford to stay in it. Mokuba liked the fact that Jasmine was around and also knew that even though his brother dated her friend Ami, he really harbored deep feelings for Jasmine. In fact, Mokuba didn't necessarily care too much for Ami because he felt she was not only stalking his brother but obsessed with him. She may have saw past his brother's cold-hearted nature but still it wasn't enough for Mokuba to say like her and accept her as his brother's girlfriend.
However, Jasmine at first wasn’t aware that Ami was in love with Kaiba and even though she didn’t like him because of how he treated Yuugi and his friends. She warned Ami to stay away from him and stop pursuing this crazy idea to be with him which they did end up dating but didn’t last long thanks to what happened between Jasmine and Seto one night at a local bar. Mokuba wasn't aware that this had happened until spying on his brother through the mansion surveillance cameras like always when he was trying to find out things his brother was hiding from him. Granted he liked the idea of his brother and Jasmine being together but Jasmine didn't seem to like the idea so well for she was involved with Yuugi.
That’s when the battle between good, evil, friendship and love collided all into one. Both girls turned evil, one to save the other and one to kill the other. When it was all over, Mokuba was still worried about his brother for he couldn't get over his feelings for Jasmine no matter how much she rejected him. He even followed her back to Tokyo to check on her and ended up getting into a car accident in the process. He got amnesia and was moved back to Domino City to recover but Ami who'd turned evil but wasn't evil anymore stuck around to help take care of his brother and Mokuba did not like that at all because Seto thought he and Ami were still dating.
He hated that so he'd decided to secretly head out to Tokyo to find Jasmine Tsukino and to see if she can talk some sense into her friend. He knows how his brother Seto feels about her so to do something nice for him, he decided to try and find out how she was doing while his brother was back home running the Kaiba Corp gaming business to even notice that Mokuba was gone. But of course it didn’t take his brother very long figure out that he was gone. Though Ami was the one that came looking for him telling him that he had to come back home to his brother. Mokuba refused because of the fact that he didn’t like Ami hanging around Seto all the time. He doesn’t love her and yet he doesn’t understand why she won’t get that through her thick skull. So he told her that if she stayed away from his brother he’d go back home.
And of course, Ami couldn’t do that so when he refused to come home, that’s when his brother flew down to Tokyo to force him to come home. Coincidentally when Seto saw Jasmine again, he remembered what all happened but come to find out that she’d fallen in love with someone else and as for Seto he felt that Ami took advantage of him while he was recovering. As much as Mokuba wanted to agree with that, part of him couldn’t since it wasn’t her fault that his brother assumed he was still dating her. However, Mokuba does blame Ami for not telling his brother the truth but he will admit that she didn’t do anything rational that appeared she was taking advantage of him.
For almost a year now both brothers have been living in Tokyo City and have set up a Kaiba Corporation headquarters in the city and had a mansion built for them both to live in. Mokuba even found himself someone to love. Well, for he feels its love but that's all entirely up to his boyfriend Mitsu Sanyu who he met during school. Yes, Mokuba became gay for whatever reason it is unknown but he feels it's a hell of a lot different than when he was dating his ex-girlfriend Maura Kiyoko. And he actually liked the new feelings he had being with Mitsu. But their relationship had its problems. For starters, Mokuba didn’t know whether or not if his brother accepted the fact that he was dating a guy and not a girl and second, he felt as if he was the only one putting in the effort make the relationship work.
Eventually, they broke it off for a few months, but got back together when the both of them realized how much they missed being with one another. He is happy that his friend Airi Ryuuga Lawliet, Jasmine’s adoptive daughter with Hideki are finally happy, starting a family of their own together. Occasionally, he will go by the Hinata Sou Inn to visit but mostly stays by himself at the Kaiba Mansion that was built in Tokyo since there was a small Kaiba Corp branch built in city which Mokuba is a representative of while his brother is continuously away on business. Because of this, Mokuba has learned to be able to fend for himself, feeling it to be wrong to take advantage of the mansion staff just because they work for him. He has proven more often than not, that he is not helpless in anyway and doesn't need his brother all the time.
However, when he does come home, Mokuba does things on purpose to piss him off for his own amusement. If he's not having sex in his brother's bedroom, the two of them are at each others throats, arguing about something. He has gone through so much that Mokuba's moods are more unpredictable than predictable. Anytime he sees his brother, he becomes immediately angry for no reason whatsoever. But in reality, there is a reason. There are a number of reasons. One being that anything that goes on in his brother's personal life that has nothing to do with the company whatsoever, he would rather not talk about it and run away from the problem instead of dealing with it like an adult.
Or he'll take his frustrations out on his brother which Mokuba has gotten completely tired of and has begun to lash out before Seto even gets the chance to. For this, they're at odds with one another. Mokuba still cares very much for his older brother but does view him as an idiot sometimes despite his intelligence. He worries that his brother will continue to bury himself in work and be alone for the rest of his life than to go out, find somebody and have some fun. But he's learned a long time ago that Seto has to realize that he can't live this way on his own. And so, Mokuba mostly focuses on his own life by going to school, running the Kaiba Corp branch in Tokyo as well as taking care of himself and the house. All while enjoying his downtime with his boyfriend.
- Mokuba had a brief relationship with a girl named Maura Kiyoko whom he did like for awhile but broke up with later but wanted to stay friends good friends with her.
- When he moved to Tokyo, he'd began a relationship with a boy named Mitsu Sanyu. He was confused about it at first because he never thought about dating someone that was the same sex as himself but he found that he actually liked it and Mitsu as well and though the two have only broken up once, they got back together and their relationship is still going strong.
- He's particularly close with his older brother Seto Kaiba despite everything he's been through and was at first mad at him for not letting everything that happened go but got over it once he told him how he truly felt about his actions about everything involving Jasmine, Ami and the Sailor Senshi.
- Mokuba's also close friends with the Sailor Senshi and often times visit the ones that live at the Hinata Sou Inn dorms as well as the other tenants that live there.
- It'd been a running gag that while living in Domino, Japan, that Mokuba is often kidnapped. This stopped when he moved to Tokyo.