Sakuya is cosplaying as Rei Ayanami from Neon Genesis Evangelion. Rei Ayanami (綾波 レイ, Ayanami Rei) is a fictional character from the Neon Genesis Evangelion franchise. She is the First Child (First Children in the Japanese version) and pilot of the Evangelion Unit 00.
At the beginning of the series, Rei is an enigmatic figure whose unusual behavior confounds her peers. As the series progresses, her personality evolves and she becomes more involved with the people around her, particularly her classmate and fellow Eva pilot Shinji Ikari. She is revealed to be a key factor in the events that conclude the storyline. Her role in this conclusion is not made clear in the TV series, but is one of the principal plot points of The End of Evangelion.