For the first time in years, the Port Mafia sends Dazai and Chuuya on an undercover mission—together. Their assignment? Infiltrate a high school in Serbia under the guise of international exchange students. Rumor has it that someone connected to an underground organization with ties to ability trafficking is hiding among the students or staff, and the Mafia wants answers.

It’s a familiar place for Dazai—he spent a significant part of his childhood in Serbia before moving to Japan. But for Chuuya, it’s an entirely foreign world. He doesn't speak the language, doesn't understand the culture, and definitely doesn’t appreciate being dragged into some nostalgic corner of Dazai’s past. Especially when Dazai seems far too comfortable slipping back into his old life.

The mission is supposed to be simple: observe, gather intel, and identify the target. But with cultural clashes, language barriers, and a school filled with secrets, things quickly spiral into chaos. And to make matters worse, Chuuya finds himself relying more and more on Dazai—not just for translation, but for navigating a world he doesn’t understand.

For Dazai, returning to Serbia means confronting pieces of a past he buried long ago. For Chuuya, it’s a challenge of patience, pride, and trust. As the lines between duty and something deeper blur, the two must learn to work together—not as enemies or reluctant partners, but as something more.

If the mission doesn’t break them, maybe Serbia will.