My Hero Academia Season 5, Episode 23, “Tenko Shimura: Origin,” focuses on the tragic story of the Shimura family. Tomura remembers his childhood. As a 5 year old, Tomura then Tenko, is abused by his father Kotaro. His father enforced the rule to “never talk about heroes.” He forces Tenko to sit outside alone without food. While his wife and her parents question his behavior they never stop Kotaro. Tenko is manifesting his Quirk, Decay. However, his constant itching is assumed to be allergies.
One day his sister Hana shows him a picture of their father with his mother, Nana. She claims to be cheering for him to become a hero, much to his joy. However, when his father finds out he’s furious. Hana lies. Telling her father that Tenko forced her to show him. Tenko is heart broken to be betrayed by his sister. While Hana’s deception is understandable, from Tenko’s perspective it’s traumatizing. His situation is made worst as his father grabs him he begs his family to he him. All they can do is watch. Kotaro tells Tenko that “heroes are people who save strangers only to hurt their families.” Then he slaps him.
He doesn’t have an itch anymore
Kotaro rereads the letter from his mother. She acknowledges that she can’t “do anything motherly,” and understands if he hates her. It’s unfair to argue the Kotaro was abused but I think he would argue he was. His abandonment by his mother caused him to become bitter and become consumed by hatred. A hate he takes out on the son who admires the hero. Tragically, Kotaro is successful in removing his sons admiration for heroes as he grow to despise them and hopes to rid the world of them.
Tenko is justified in his hatred of his father and his useless family. However, he’s cursed with a Quirk that can only be destructive. His Decay ability finally emerges when he’s petting his dog, Mon. By killing his only support (his dog), Tenko panics. He assumes a villain killed Mon. Watching the tragedy unfold was heartbreaking. As Tenko recounts this moment, he kills his entire family from the most innocent, Mon to the most guilty Kotaro. By the time he murders his father he’s no longer Tenko Shimura.