Detective Boys is the 10th chapter of Bungo Stray Dogs.
Atsushi's kidnapping has been reported to the Agency, but they are busy with another case before the director tells them to drop it and focus on finding Atsushi. Ranpo had to be coaxed by the director to help. Meanwhile, Chuya Nakahara, Dazai's ex-partner, visits Dazai to ruin his plan and duel with him. Dazai reveals that he could have escaped all along. Tanizaki tracks down the company that owns the truck that Atsushi was kidnapped in, but discovers that all the employees were killed by Akutagawa. Ranpo is finally convinced to use Super Deduction to help with the case. He deduces that Atsushi is on a ship at sea, and it's sailing away. Kunikida rushes off to the Agency's boat at the port to go after it.