Manga by author Morita Mario

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! [from paramitan of MangaHelpers]

Original webcomicFrom MangaHelpers:Ichijo Kazuya thought that he was murdered, but when he came to, he was back in his high school days. He lived his entire life as a playboy and had had countless sexual encounters with women until that fateful day that he was killed. He realizes that his murderer was his old high school friend Tanaka Masaki who was jealous of Kazuyas relationships and his built up anger eventually exploded. Taken back 15 years into his past, it seems that he has been given a second chance at life and given a chance to make different choices. He decides that the way to prevent his eventual demise is to make sure Masaki is more successful with girls and loses his virginity before Kazuya. But fate seems to be steering Kazuya towards the path of his previous life and keeps introducing the same girls he had sexual encounters with. [vyc]