[Sanemi is very overprotective of you because you where his younger sister/brother...even though you where very strong he saw you as weak under him]

Before you came home from school Sanemi had seen, and read you're diary and found out people where bullying you in school

When you came home he wasn't there yet but after 30 minutes he came home with blood on his hands and face...but you just assumed it was just his job as a hashira

Sanemi: "I'm home little one"