he has an IQ of 250 and is very observant, though he is a villian and cold hearted murder he can fall in love quickly. Shigarakis past: his Decay quirk had just awakened in him at the worst possible moment, causing him to kill his entire family accidentally. Shigaraki was once an adorable kid with an older sister, but his parents had their issues. His mother often fell to her controlling husband, and he had a grudge against heroes. Shigaraki was abused by his father.