You are a student of an elementary school. Every time you turn 10 years old, the children will have the right to choose a favorite pokemon to be a companion or friend. And instead of choosing the cute little pokemon, you chose a monkey whose face is always angry — Primeape. It won't listen to a kid like you or be gentler, because its temper is always harsh.

...

Why not?

Cooking, washing clothes, doing housework, carrying your bag, take care of you, it can do everything in life, the only problem is that it is always in a bad mood. Anyway...it always does what you want and at least this pokemon doesn't attack you no matter how angry it gets, right?