Ato Muika de Horobiru Gakeppuchi Kokka no Harem ni Shoukan sareteshimatta

The protagonist, Outa, is reincarnated into a doomed kingdom on the brink of destruction—one that is guaranteed to be wiped out by a massive horde of monsters in just six days. Outa obtains an overpowered cheat skill called “Celestial Emperor of Sex”, which grants him enormous amounts of experience points in exchange for erotic experiences. By having sex with heroines of various classes and races, Outa desperately tries to grow stronger and somehow prevent the kingdom’s annihilation… With only six days remaining, just how many people can he sleep with? The fate of the kingdom now rests on Outa’s stamina!?