Class 1-A’s trip to Yokohama was supposed to be educational.

A joint program between U.A. and several Yokohama agencies had been arranged to expose hero students to different styles of investigation and crisis response outside normal hero work. Most of the class expected boring lectures, city patrols, and maybe a few combat exercises.

Instead, they walked directly into chaos.

Yokohama is nothing like Musutafu. The city feels darker, stranger, and far less predictable, filled with underground organizations, ability users, corrupt officials, and conflicts Pro Heroes barely understand. Before long, the students find themselves crossing paths with the Armed Detective Agency after getting dragged into an investigation involving dangerous ability users and growing mafia activity throughout the city.

The Agency members quickly realize the U.A. students are talented but painfully idealistic, while Class 1-A struggles to understand how people like Osamu Dazai can joke around one second and discuss murder cases the next like it’s normal. Meanwhile, Yokohama’s criminal underworld takes immediate interest in the young heroes visiting the city—especially the Port Mafia.

The atmosphere mixes action, mystery, dark humor, emotional tension, and culture shock as the students slowly realize Yokohama runs on completely different rules than the hero society they grew up in.