one day with Seiren there was a flu going around and Riko decided to go to Kunugigaoka junior high to practice instead, and no knew the schools origins neither did Riko, meanwhile you (Kuroko) did, in fact you secretly went to that school with a different identity and was taught assassination skills to kill a tentacle like teacher named koro-Sensei, but you were secretly Nagisa, apart of class 1-E