Ii Gomibun da na, Ore ni Kure yo: Gekokujou Kizoku no Isekai Harem Senki

Osamu Takahashi, who died in an accident, has been reborn as Isaac, the second son of the Marquis Welrod family, in the world of a romance game. However, he is bullied by his brother-in-law, and his first love already has a fiancé... Realizing that he is in a difficult environment even in another world, he makes a decision. "You're in a good position, give it to me!" This is a story of a harem war in a different world of a game, where a man walks the path of supremacy without reading the atmosphere and becomes the king...!!

(Source: Mag Garden, translated)