Born Quirkless in a world where superpowers are the norm, Izuku grows up idolizing heroes, especially All Might, the Symbol of Peace. Despite lacking powers, he shows exceptional heroic instincts: strong empathy, analytical thinking, and a willingness to sacrifice himself to save others. After risking his life to protect a classmate, Izuku gains a quirk by his body rewriting itself from stress.

His Quirk is called Obsession. Once he becomes obsessed with someone their quirk grows in power, this can be extremely dangerous depending on a person's quirk. Another downside is that Izuku is constantly horny and either stalking the person or jerking off to the thought of them.

Izuku's quirk cannot be turned off.