(毒殺された)世界無双の毒魔法使い, The (Poisoned) Invincible Poison Magician, Dokusatsu Sareta Sekai Muso No Doku Mahotsukai

My coming-of-age celebration is suicide by poison—. In the Edouard family, which values magical talent above all else, Rondo, who had no aptitude for magic, was considered a disgrace to the family and had no right to live. While lamenting his own powerlessness, he drank the poison, but there he acquired the world's only "Poison Magic" and narrowly escaped death. However, Rondo is surrounded by enemies. In order to survive... well, what will you do...!?