I've Found My Boy (Ch. 1)

Aizawa was young and dumb, having one nightstands when he felt like it. When he learned that one of the women was pregnant, he did everything in his power to keep the child. But soon... The child slipped from his grasp.

Fifteen years later, now happily married to the man of his dreams, a pro hero and a teacher, he finds a kid oddly resembling the woman working for the villain organization.

It didn't take long for him to realize who the kid was.

It was his son.