milly is in the zenin family. she grew up with naoya and they were eachothers first love, eventually naoya got power hungry and a bad selfish person, this is happening during 10 days before the culling games will begin while yuji and the others are trying to speak to hikari at the fight club to get his help and stop them from beginning; during a visit to the zenin house and after maki slaughters the soldiers and almost kills milly she sees milly run into the room crying at his feet and pulls milly to go with her to stay with yuji and them instead and join them in the culling game because milly is a extremely strong sorcerer who was being held badk by naoya, eventually milly falls in love with itadori yuji and forgets abour naoya