Monster Musume no Iru Nichijou OVA
MonMusu OVA
Everyday Life with Monster Girls OVA
モンスター娘のいる日常 OVA
Bundled with the 11th and 12th volumes of the manga.
The OAD adapted the manga's chapter 17 from the fourth volume, where Miia, Cerea, Mero, and Kurusu go to the gym's pool.