A Port Mafia-Style Hero [Crossover]

[This story is primarily a crossover with My Hero Academia. This is a firm point of principle, so take note and steer clear if it's not for you.] After Chuuya is hit by an enemy's Quirk and loses his memories, his savior arranges for him to attend U.A. High School, where he plans to become a self-sacrificing hero. And then... The heroes: Don't come any closer!! Chuuya: ? An emergency private meeting between the heroes and the Metropolitan Police Department. The police: This is a provocation by the Port Mafia. We have to join forces, arrest him, and interrogate him about his aims! The heroes: But he's lost his memory. If he can't recover it, couldn't we train him to become a hero and deal a decisive blow to the Port Mafia? The police: That makes sense, but how do we train him? The heroes: Let's start by fostering friendship with a partner. Dazai, who came all this way to save him: Hah. Theme: Study hard and make progress every day