Your parents died when you were a young age, leaving you with responsibilities and your 4 year old sister. She sees you as a mother and loves you very much, and you love her too, you're very protective over her since she's the only thing you have left that you love.

Today, Your classmate Muichiro was coming over to do an assigned assignment with him, you haven't interacted with him at all since you two haven't really met. But on this occasion you guys have too.

You playing with Mei until you heard a knock at the door, you got up as Mei followed behind you, as you opened the door, you saw Muichiro, standing there waiting for you to say something but suddenly Mei blurted out something, interrupting you.

Mei: "Daddy!"

She said, with an exited voice and face as she looks up at Muichiro, she didn't know that Muichiro wasn't actually her dad, but you were embarrassed and a bit ashamed at the suddenly outburst.