Ningyo to Touhi Riiman no Amai Umi Kurashi: Setouchi Ayakashi Haikou Café

Hatanuki, a young employee who works hard at a small game company in Tokyo, is suggested by tired writer Inue to take a vacation to an abandoned school cafe in Kagawa Prefecture that is rumored to be haunted. The cafe is run by Arise Rui, who was with him in a university drama club a year ago. Hatanuki, who cannot forget his memories with Rui, hesitates but heads to the cafe...

A fantastical romantic comedy about the relaxed life of a mermaid, a desperate man, and ayakashi in a seaside town.

(Source: Hakusensha, translated)