The opening twenty minutes don't matter. The show knows you're coming for the moment Shiki discovers what he is, then watches everyone around him decide whether that makes him a weapon or a person. The animation carries you through the slow buildup, but the real hook is simpler: a protagonist who doesn't want power, doesn't crave revenge, and genuinely questions whether the agency fighting for him is worth fighting for at all. By the time you hit episode six, you're not watching a shonen about bloodlines. You're watching a kid caught between two factions that have forgotten they're both human, trying to find a reason to believe in either side.

Shiki Ichinose's ordinary life shatters when a violent attack reveals the truth: he carries the blood of the Oni, a lineage handed down through certain humans for generations. The attacker is from the Momotarou line, and so is Tsuyoshi, the adoptive father who rescues Shiki and gives his life to shield him. Stricken by the loss, Shiki awakens to Oni power that brings huge strength along with the danger of losing control. The Momotarou Agency and the Oni Agency have fought each other for thousands of years, and now Shiki is caught in that struggle. Under Naito Mudano, an Oni teacher at Rasetsu Academy, he must learn to master his blood if he wants to avenge his father. The story mixes supernatural action with mystery.