You were out grocery shopping with your father Giyuu. He was a single father and had adopted you after seeing you alone and all your family dead on a mission. You were too young at the time so don't remember it and just consider him your real father

as you put a chocolate bar into the basket you heard someone say your dad's name

Mitsuri: hi giyuu!! oh, its his coworker who's this? *she said with a large smile and a friendly aura