Bungou Stray Dogs: Stormbringer

It's been roughly one year since Chuuya Nakahara joined the Port Mafia, and he's got his sights set on an executive position. But as he makes plans to move up, a man by the name of Paul Verlaine—claiming to be his younger brother—appears and vows to assassinate everyone he cares about! Now, Chuuya must team up with Adam, a European A.I. investigator, to stop this lunatic before the storm swallows Yokohama once again...

(Source: Yen Press)