His father married too young, so his son took the risk to seduce his stepmother

It's been five years since my mother passed away and I became a motherless family. Naoki did housework in his free time from school and lived next door to his father. One day, when Naoki came home, he found a sumptuous meal at home and a young woman. It was Mika, who used to be his father's secretary, who heard the story. “Dad has decided to remarry Mika.” A young beauty suddenly becomes a stepmother. …It was inevitable that Naoki would consider Mika a woman.

His father married too young, so his son took the risk to seduce his stepmother