OBA-354 From today, this person is your mother. Shimazaki Kasumi.

One day, my old man brought a woman home and said, 'From today on, this person is your stepmother.' I couldn't accept it, so I asked my friend Satoshi to bully her. But I never thought he'd do something like that―. Satoshi had sex with mom. I couldn't forgive him, so I got into a fight with Satoshi. He was no match for me, but I couldn't forgive him. And seeing me covered in bruises, my stepmother gently comforted me... not as a stepson, but as a man...