Bungo Stray Dogs: Wan! (2015)

Blurb:
From the pages of “Bungo Stray Dogs” comes a new series about the peaceful, everyday lives of the cast – only now, the Armed Detective Agency and Port Mafia are mini-sized?! Whether it’s sniffing out the dark secrets hidden in the agency lockers, or going to a public bathhouse with the Mafia barking at their heels, there’s never a dull moment for Atsushi and his friends!

Source: www.anisearch.com/manga/31333