From MangaDex:

The mom characters that appear in the game are all unfortunate sub-heroines who always get bad ending routes. “Why… Why does such a cute mom have to die?!“ Even though the protagonist tried very hard to request a route where they get saved, all of his efforts were in vain, making him spend his days in frustration. Then, he suddenly gets reincarnated into the world of MamaFan on a certain day. …However, he gets reincarnated as a villainous aristocrat who’s got nothing but the worst routes. This guy, who’s crazy about mom characters — his fulfilling days of saving his beloved mom characters and his journey to create his harem full of plump women are about to begin!