Mama Wa Doukyuusei

Ever wondered what it would be like if your mother was in your class? Ryou Kisaragi does. Actually the mother to be is none other than his classmate Imai Yuka: a girl who he saw naked in his house one morning, and who is father is remarrying.
Now he must juggle his desire for his soon to be step-mother and his love for his girlfriend! WHO WILL WIN OUT!
-from baka-updates: “About a high school guy who finds out that his new step mother is none other than a classmate from his school.”