Tadashii Kodomo no Tsukurikata!

正しいコドモの作り方！

The future where the Virus of Death shall destroy humanity awaits. In order for humans to avert that destiny, Raito is asked to travel back to the past. His mission: to make sure a normal high school freshman Tanaka Yuu makes children with his childhood friend Takane Kyouko! (Source: MangaHelpers)