Do You Love Your Mom and Her Two-Hit Multi-Target Attacks? OVA, Do You Like Your Mom? Her Normal Attack is Two Attacks at Full Power OVA, Okaasan online OVA
Unaired 13th episode.
To thank the group for all their hard work in the past, Shirase invites the party to enjoy the sunny beach. While enjoying the wonderful weather and pristine waters, an accident causes Masato to lose all his memories, including those of Mamako!
(Source: Funimation)