Sayaka is a girl of average height with long dark violet hair that has bangs swept to the left and styled into a side ponytail tied with white ribbon, empty dark violet eyes and light pink lipstick. She wears the Hyakkaou Private Academy issued uniform: a red blazer with black trim lining the cuffs and collar, a white button up dress shirt, a dark pleated skirt that is slightly longer which stops above her knees (than the other female students), a black string tie, black socks that go below the knee and brown loafers with black soles.
While in middle school, she was wearing black glasses and had her hair styled into two pigtails.
PersonalitySayaka is a very intelligent and serious girl, who deeply cares about the school and Student Council. She worries a lot about what happens to the school. She is also endlessly loyal to the Student Council President. She stated, that Kirari is her one true love and she would do anything for her. Kirari states, how much Sayaka is driven by logic. Her and Kirari's wildly different personalitys seem to be what attracts them to each other.
While she seems to be reserved and calm, her subduing of a violent student, Jun Kiwatari, and telling him what he now owes in the debt recollection game shows that she's every bit as terrifying as the rest of the Student Council. She's also jealous of Yumeko Jabami for capturing Kirari's interest and views her as a plague. Thus when something threatens Kirari or the school she gets very enraged quickly.
During middle school and her first year in high school, Sayaka was a shy and nerdy girl who's spends her time only on studying. Despite being the one with the highest grades in the entire school, she was pretty unpopular and didn't have any friends.
Two years before the Yumeko Jabami's transfer, Sayaka witnessed a gamble match between the former Student Council President and a first year transfer student named Kirari Momobami over a Student Council President position. Sayaka was impressed by Kirari's victory to the point where she applied her CV to the Student Council in hopes to become a personal secretary of Kirari, now the Student Council President. Finding Sayaka interesting, Kirari agreed to hire her, giving her a little makeover in the process.
Kakegurui - Compulsive Gambler
Sayaka is first seen after a gamble between Yumeko Jabami and Itsuki Sumeragi, where she was observing the whole match from the distance. She then goes to the Student Council office to announce the defeat of Itsuki. A day after Yuriko Nishinotouin's defeat, she came in and presented the Mary's lifeplan to Kirari. When Mary stormed in wanting to talk to Runa Yomozuki about her lifeplan, Sayaka remained silent, even when Mary started screaming and thre her lifeplan around.Soon after, Sayaka was explaining and managing the debt-swap game. She announced how the game was a way for housepets to climb back up. She then observed the game between Yumeko, Mary Saotome, Nanami Tsubomi & Jun Kiwatari, specifically because the president wanted to learn more about Yumeko. Sayaka was impressed by them playing. She was surprised when Yumeko wanted not to report Jun's cheating and simply to carry on. Sayaka accepted and continued to observe. She also reminded Jun multiple times, that violence is forbidden.When Jun wanted to attack Yumeko, she tasered him. She informed him that he was now a housepet and in debt to the council. She later visited the empty council room and layed down on Kirari's chair, worrying about the future of the academy and that Yumeko might be dangerous for Kirari's perfect garden.
So Sayaka decided to gather some information on Yumeko, which she then presented to the council. She stated that Yumeko has a sister, who is currently hospitalized and Yumeko is paying the costs. From that she deduced that she must be extremely rich and purposefully stays a housepet. All of them then fear that she wants to challenge Kirari to an official match. Later that day, Kirari leaves with a helicopter. Sayaka is worried and tells her to stay, since Yumeko had just beaten Midari Ikishima in a gamble. But Kirari tells her that is the exact reason she must leave.Everyone is still worried, but Yumemi Yumemite announces that she will take care of Yumeko and defeat her live on stage. During her gamble she sat in the audience with the others. She was still worried about the school and what would happen, especially when Yumeko won and challenged Kaede Manyuda to play. When Kirari later revealed herself to be the president, she was extremely shocked. She went down on stage to do her braids, but stayed silent. Sayaka was conflicted and distraught, not knowing what to think. After that game, Yumeko and Kirari played the Tarot card game. Sayaka also watched and was afraid. When it ended in a tie, she was relieved and hugged Kirari, who said everything will be fine now.
Sayaka didn't take a liking to the presidential election, especially with the Hundred Devouring Families being present too. She feared that Kirari Momobami would lose her position and had to leave the school. She tries to call out Kirari, but couldn't change her mind. During the gambles, she stands next to her, threatening others that get to close, like Horo Jomaru with a taser.
She is later seen telling Kirari, that Terano Totobami has already acquired 168 votes. She offers Kirari to eliminate every threat to her. But Kirari denies and enjoys the thrilling situation and wants to see more from Yumeko Jabami, which somewhat breaks Sayaka's heart and she feels jealous of Yumeko. So, she calls her out as a pestilence during the life broadcast and challenges her to a game of life and death. Kirari is excited by this and suggests the Tower of Doors. If Sayaka loses, she will not only die but she will also be a stranger to Kirari. This would be the worst nightmare of her and means she bet everything as Sayaka is determined to beat Yumeko. They have to solve the riddles in order to traverse through the tower. Sayaka quickly figures out the first solution and advances one floor deeper. She is even at the first floor quicker than Yumeko. When Yumeko also appears, Sayaka has to hold back laughter. She believed to have totally overestimated Yumeko.She is still determined and climbs the Tower in the perfect time. But Yumeko is already there, because she figured out how the tower worked. This meant Sayaka lost and had to jump. She was absolutely crushed. She chose one of the outer doors and subconsciously took the one, whose answer is 5, because the Tower had five floors. She stated her love for Kirari one last time and jumped. She already accepted her death, but Kirari jumped after hear. Sayaka was terrified, thinking Kirari would now die too. But they landed on a safety mat. Kirari laughed and Sayaka was still shook. Kirari proceeds to tell her, that she is absolutely fascinated by her and how she acts only logical. Kirari then again asks her to become her secretary, since they are now strangers. Sayaka has now learnt, that she will never be able to truly understand her, but that is exactly where their feelings come from.
When Terano later discusses with Kirari about Rei Batsubami's possible climb to the top of the clan, Sayaka mentions that being devoured in an interesting way can be enjoyable as well. This goes to show that she has learnt to stray more from logic and is able to think more like Kirari. When Terano later surpasses Kirari in terms of votes, Sayaka resorts to buying votes for 8 million Yen from students, in order to secure Kirari's seat. She sell 280 million to Jun, who came back to get rid of his housepet rank. She then talks to Kirari how she will compete with Terano in buying votes and she is happy to act as one of Kirari's fishes in her aquarium.
Kakegurui (Kakkokari)In the spinoff manga, Sayaka is usually the "straight man", having to deal with the other characters' weird antics. Like in the main series, she deeply cares about Kirari Momobami as Syaka is often at Kirari's side and supports her. She's often worried about her wellbeing as she feels guilty when Midari Ikishima is trying to scare Kirari with a surprise toy box and makes her gamble on what her reaction will be. The two are shown to be close friends, even though Sayaka is usually unamused by Midari's behavior. In a chapter, she unsuccessfully asks her to stop using the projector belonging to the student council to watch animal documentaries. In a different chapter, Sayaka tries to teach Midari how to be less vulgar but ends up feeling embarrassed by her choice of words. Sayaka is also shown to be very jealous of Kirari, for example when she announces she will get married soon as a prank.
Kakegurui - Compulsive Gambler
- A Girl named Yumeko Jabami (cameo)
- Boring Girl
- The Slit-Eyed Girl
- The Girl Who Became a Pet
- The Girl Who Became Human
- Tempting Girl
- Refusing Girl
- Love-Dancing Girl
- Dreaming Girl
- Selecting Girl
- The Girl Who Bets Her Life
- The Girl Who Gambles Compulsively
- Gambling Girls Again
- The Girls of the Momobami Clan
- Communicating Girls
- The Girl who Changes (flashback, non-speaking)
- The Winning Girl
- The Girl by her Side
- The Logical Girl
- The Null Girl
- The name Sayaka means "pureness" and "flowers" respectively.
- Sayaka's surname Igarashi means "fifty storms".
- It could be possible that Sayaka is ambidextrous:
- The game Sayaka played against Yumeko Jabami, the Tower of Doors, plays out during the election in the anime.
- In the manga, that game was played in place of the Tarot cards.