Based on the manga series from One-Punch Man creator ONE, the series follows Mob, an 8th grader with powerful psychic abilities working under his not-so-capable master, Reigen. Mob uses his powers to exorcise evil spirits, but because of his will to be normal, it causes him to suppress his powers and feelings until he hits 100%, a point where his pent-up emotions are unleashed and a darker power takes over.
[Source: Anime News Network]