Shikkaku Kara Hajimeru Nariagari Madou Shidou! summary:

Let me tell you the story of Arcs Reytheft. A great feudal lord’s disgraced eldest son. Because he was weak, he his family left. And so he strives to become the strongest one. For you see, Arcs was once a Japanese man. And got sent to this world as soon as he died. His father wanted to have. Arc inherit his land. But in terms of magic, he was disqualified.The background is set, and Arc’s goal draws near. Get back at the people who mocked his weak skills. Whether by training or cheats? That part is unclear. But who cares? It’s time for some self-insert thrills.