Tamatteru no, Mama ga Dashite Yarushi ♪ ~Kuro Gyaru Mama no Doutei Choukyou Lesson

My peaceful life vanished in an instant. Rewind to one month ago— Out of nowhere, my dad brought home his new wife. She turned out to be a junior at the same school as me, one year younger. Her name was Yukina. She had dyed hair, tanned skin, and a carefree attitude—your typical "gal" type of girl. A girl like her, flashy and outgoing, was the complete opposite of someone plain and unremarkable like me. That’s why I tried to avoid getting involved with her as much as possible in our new living situation… But between their constant, sickeningly sweet displays of affection and the sounds of my dad and Yukina getting intimate almost every night, I was left in a state of constant frustration. Then, one day, something happened. Yukina barged into the bathroom and started toying with me! "Hey, I just had a great idea. In exchange for doing the housework, I’ll teach you a thing or two, virgin boy♪" Yukina—my stepmom, my junior at school, and a so-called "gal." And now, I’ve become the target of her "games." What on earth is going to happen to me from here on out…!?