Sayu’s current skills are pretty much trying to be as nosy as possible in others private matters which she usually teases them about it. This is mostly done to her brother Raito since he’s a high school student. She's also good at photography and tries to use her brother in most of her projects, even if he refuses. She is more close to Nunnally Lamperouge, making sure that the other girls in their class don't try anything stupid to bother her. Sayu's very overprotective towards the friends she has and will not let anyone or anything harm them in any way. She strives hard to do good in her own way and accepts the fact that she can still be the best without having to be intelligent like her brother.
Sayu is not very strong when it comes to academics and usually has to ask her teachers for help or not that she asks Raito since he’s way smarter than her which she says he’s lucky he’s born smart. She has a habit of constantly asking her brother for help with her work. She also doesn't like it when other students use their family's background to act as if they're better than anyone. Sayu won't hesitate in a heartbeat to tell someone off and put them in their place. This is why she prefers not to hang around a bunch of snobbish rich kids because she finds them incredibly annoying that they flaunt their money around to get what they want as well as buy their way out of any jam they're in.
Originally, Sayu was 5'2 with long brown hair that goes all the way down to the middle of her back but she'd always wore it in a ponytail and brown eyes. Now, over the course of the semester, her outer appearance has changed quite a bit. She is much taller, now at 5'4 her long brown hair cut short to where it stops at the nape of her neck and she wears a black ribbon to keep her hair out of her face. During her now senior year, she has grown her hair longer and has small curls at the ends with her bangs swept to one side. Once originally very flat-chested, now fully blossomed out with her bust size at a B cup. She has a very bright peach skin complexion that comes across as pale in different shades of lighting. She wears the Juuban Municipal Academy's girls uniform for her grade level, which is a yellow jacket, white long sleeved shirt, green tie, black skirt and brown suede shoes. When not wearing her uniform, she's usually seen wearing more casual attire like a long sleeved off the shoulder kind of shirt with black tights underneath or jeans with a tank top, skirts or shorts in a variety of colors and for footwear, would sport either sandals, sneakers, or platform shoes.
Sayu Yagami is your typical school girl in a practically perfect family. Raito Yagami is her older brother who is currently attending Todai University is a genius who she envies and at the same time admires. Unlike her brother, she was not born gifted and is hardly above average when it comes to academics. The only thing she participates in at school is the photography|art club. Sayu mostly sends her free time, if not bugging her brother to help her with her homework, she's teasing him about his private life and being nosy wondering if he has a girlfriend or not. Her Sachiko, her mother, is a stay at home mom, mostly taking care of the house and her family while her father Soichiro works all day and night as a police officer to provide for his family. All the while, Sayu he loves to rock out and party whenever she's invited to parties by her friends. She enjoys taking pictures since she's been taking her photography class at Ashford and is staying after school taking lessons from her art teacher to improve more to make her photos look better and cooler. She also does a little dancing and singing here and there but only when she's hanging with friends and just to goof off for fun. Photography is about the only thing that she works hard in school at doing. Which her family supports but her parents wished she'd improve more in her academic related classes more.
And although her father is the chief of police, she doesn't use that to get over on people like most would. And she doesn't look down on others either just because they don't have connections, not popular or rich. Sayu won't hesitate to tell someone off about themselves who feels they're better than everybody because of their social status. She hates it when a person uses their background to feel as if they can get away with doing and saying anything they want to people. She's particularly fond of hanging around her young classmate, Nunnally Lamperouge, who's the same age as her. The only thing is, Nunnally is blind and cripple, unable to do things that Sayu and others can. Because she hangs around her, Milly took it upon herself to make Sayu an honorary Student Council Member. Meaning now that she has to be involved in particularly anything crazy that the older girl comes up with.
Sayu is more than happy to do it though. Plus, she felt that she was Nunnally's personal bodyguard to keep the morons away that try to pick and tease her because of her disabilities. She's also unaware that her friend is in fact rich and her grandmother is the Vice Principal of Juuban Municipal Academy. Even if she knew, it probably wouldn't change much. She'd still be by her side no matter what happens or changes in the years to come. In short, Sayu's not a very hard person to make friends with, she's very nice, polite and not rude. She only snaps when she feels that someone's being out of line. She's mostly walking around with a camera from the art room in her hands and wears different attire to as she puts it, 'set the mood' for her pictures that she takes.
Also, she's glad her parents aren't pressuring her to be as smart like her brother, preferring to being more relaxed and content with herself. And now that Raito has himself a girlfriend, a young woman by the name of Ami Mizuno, she often harasses him with the subject of marriage as she wishes the two of them would just go and get married already. She wishes the same thing for herself but of course, that'll be years from now. Until then, she's more content with enjoying life as a teenager and praying that her school years don't come to an end so quickly. After all, there's still so much Sayu wants to do and feeling she has only so little time to do it. But as long as she has her best friend Nunnally with her every step of the way, she'll be more than happy.
Sayu shares a close friendship with Nunnally Lamperouge, like a surrogate sister as she stands up for her when others try and make an attempt to put her down and ridicule her because of the simple fact that she is crippled. She doesn't consider her to be crippled but a regular person just like everyone else. She treats her no different that she treats anyone else who isn't wheelchair bound. However, her closeness to Nunnally could make some think that Sayu is either a lesbian or bisexual at the least because she does show an interest in guys, stating that Judai Yuki was cute when her and Nunnally went to take a tour of Tsukuba Academy.
- Sayu is the new Student Council President at Juuban Municipal Academy. Sayu pretty much takes Rivalz from Code Geass's role regarding this position since all of the original members of the Council have left.
- Sayu displays hints of bisexuality because of her close relationship with Nunnally but at the very least, she does appear to be heterosexual as she comments on who cute guys are frequently.
- She is the younger sister of Raito Yagami.
- Sayu approves of her brother's relationship with Ami Mizuno because of the simple fact that she's happy to know that he finally decided to start dating and was worried that he'd be too consumed by studying all the time to even consider starting a family of his own much less having a girlfriend.
- Sayu is unaware that Ami Mizuno is a Sailor Senshi.