One-Punch Man (2015)

S1E6 The Terrifying City

Five days have passed since Saitama officially became a professional hero, but he hasn’t had a single heroic moment. When Genos tells him that C-class heroes who remain inactive for a week are removed from the hero registry, Saitama decides to take action. He sets out to patrol the city, but despite his efforts, he encounters no villains or monsters to confront.