勇者の当て馬でしかない悪役貴族に転生した俺 ～勇者では推しヒロインを不幸にしかできないので、俺が彼女を幸せにするためにゲーム知識と過剰な努力でシナリオをぶっ壊します～

I was reincarnated as a villainous nobleman who was nothing more than a foil to the hero. As the hero, I can only make my favorite heroine unhappy, so I will destroy the scenario with my gaming knowledge and excessive effort to make her happy.