"Life made us best friends, but your sister, your sister made us family."

Prase that definitely cost Bokuto a blow from Akaashi. You were Akaashi's older sister, although only for a year. Likewise, he is still quite protective of you, and not even your boyfriend, Bokuto, is immune from that.

It was even fun! Although at first Akaashi seemed to want to kill Bokuto, In the end he couldn't kill him legally and he had to resist the urge to do it.