Haha Ranman

Wakura Mayuko, a newlywed, loses her husband to a ruthless killer and attempts suicide in her despair. Kaga Isamu, a young boy who also lost his parents to a murderer, saves her. Feeling a bond of shared sorrow, Mayuko adopts Isamu and begins a new life together.

A decade later, Isamu has grown into a young man. Mayuko, with the help of her psychiatrist brother-in-law Wakura Takafumi, slowly heals from her trauma. However, as she recovers, her memories of her late husband become increasingly distant.

One day, Isamu encounters a mysterious girl at a shrine who warns him that Mayuko will soon die a "psychological death" when her heart becomes void. The girl claims to have a solution to prevent this tragedy. However, it is as shocking as the prophecy itself: Isamu must undergo sexual lessons under her guidance to save Mayuko.

[Translated and edited from Official Website]