A character from Blue Archive, she's the president of the Xuanlong Office and the student council president of the Shanhaijing Secondary School.
Her full name is Ryuuge Kisaki.
The trend of drawing her performing the "Banzai stretch" originates from episode 3 of the in-game event Catch in Neverland, where Shun makes fun of Kokona for performing them, also stating that Kisaki had previously tried them before and had deemed them useless.
Her outfit consists of a short black sleeveless china dress with a back cutout, a side slit a pelvic curtain and a dragon print, a grey vertical-striped coat with pinstripe pattern, black half gloves and black pumps.
Original artist: yutokamizu