From September Scanlations:

Pairing: Nanase Haruka/Matsuoka Rin

On patrol one evening, Officer Matsuoka Rin comes across a man collapsed on the beach by the harbor. The man has no identification on him and cannot speak, so Rin takes him in, as he has nowhere else to go. But “Nanashi-san”, as the man comes to be called by Rin’s friends and family, is strange – how did he come to be washed up on the shore, why can’t he speak, and why does he at times behave less like a human…and more like an animal?