Well, you could say there are hints of love here and there. But it's not a conventional love story. The series is primarily known for its action and supernatural elements with love being a secondary aspect.
Bungo Stray Dogs is both. It began as a light novel and then was transformed into a manga. The light novel provides detailed storytelling, while the manga brings the characters and scenes to life visually.
Typically, characters like Dazai Osamu are central to the 'bungo stray dogs' series. In volume 15, he might still play a major role. Also, characters who are part of the Armed Detective Agency and the Port Mafia are likely to be prominent. For example, Kunikida Doppo from the agency, who has his own set of ideals and abilities. But again, this is based on the general pattern of the series and not definite for volume 15 without reading it.
Chuuya Nakahara is also very interesting. His short - tempered nature combined with his powerful ability, For the Tainted Sorrow, makes him a force to be reckoned with. His relationship with Dazai, which is full of rivalry and a strange sort of mutual understanding, further enriches his character.