An adult reincarnates with full memory and refuses to be the genius wanderer, he wants to be cunning, calculating, happy. That shift from "strongest" to "smartest about what matters" is the entire show. Seika knows the trap of power and walks around it anyway, which sounds simple until you realize how rare that actually is in isekai. The writing wavers later and forgets what made him interesting, but those early episodes hit because they let a grown man choose a different life instead of repeating the same one with better stats.

Haruyoshi Kuga stands at the pinnacle of his world: an unrivaled exorcist whose mastery of onmyou arts has no equal. Yet strength alone hasn't brought contentment. When the Imperial Court betrays him and leaves him near death, he resolves to find happiness in his next life. He activates a secret reincarnation technique of his own design, betting everything on a second chance. He is reborn in another world as Seika Lamprogue, an illegitimate son of a noble family proud of its magic. Judged to have no magical ability, he is largely ignored by his relatives. Seika soon finds that the magic of this world pales beside his old arts, and with demons and youkai at his side, he sets out with a crucial lesson learned: this time he means to be more cunning. Wary of repeating the mistakes that ended his past life, he hopes for a peaceful existence rather than hollow achievement.