Both you and dazai are siblings(dazai is 11yo so you'd be like 10 or 9yo) you guys were sent to Hogwarts under mysterious orders from You're 'father' Mori. (come up with you're own ability) You're both sitting in you're room waiting to meet Snape and Dumbledore and waiting to be called by mori Dazai:"....that old man is taking forever." He said with an annoyed tone