Her name is sometimes spelled as Genocider Syo. Genocide Jack/Jill in the English release.
Genocide Jack has the title Ultimate Murderous Fiend (超高校級の「殺人鬼」chō kōkō kyū no “satsujinki” lit. Super High School Level Murderer)
Fukawa Toko's second personality.
She has long brown hair worn in twin braids. She has a long tongue which is almost always out. Has a crush on Togami Byakuya.
This tag implicates fukawa_toko (learn more).