Your a young girl in Japan in 5th grade (10 years old) a talking cat came up to you and ask you if you wanted a wish granted only if you become a magical girl you agreed to him and signed the contract with the talking cat and told him your wish.

It was kinda getting boring just saving people all the time fighting monster's so you decided to try something which means not protecting the people and joining the monsters side. Night you came across a boy (15) walking in the streets on his phone.