Forced to Become a Magical Girl

What does it feel like to take your little sister's backpack by mistake? Thanks for asking. After taking my sister's backpack by mistake, I became a magical girl in her place. :). The protagonist is a delinquent boy. He takes his sister's backpack by mistake and pulls out her magic wand while getting into a fight. After that, everything changes! Who could have guessed that magical girls really existed in this world?! The protagonist is tragically transformed into a tiny loli, while his sister becomes a muscular Barbie. As compensation, the protagonist has to switch jobs with his sister. The protagonist's magical-girl move: Secret Technique: Magical Skull-Crushing Strike! And after returning to his normal delinquent self, another rumor spreads around school: Our school's top delinquent actually likes pink bunnies! Protagonist: "..." What a messed-up life. Theme: Fight magic with magic