Kokoro ga Mizugi ni Kigaetara.

Kokoro ga Mizugi ni Kigaetara. ("If Kokoro changes into a swimsuit...") is a side-story episode to Onna no Ko to Misshitsu ni Itara ○○shichau Kamoshirenai featuring the same gameplay. Kōhei finds himself once again in the dream world with Kokoro, who has become trapped in her own bedroom while trying on a new swimsuit. The player must use Kōhei's spirit powers of suggestion to help her break the seal on the door.

This episode includes a single room to escape, and is playable completely independently of the main game. It was included as a bonus download code with initial copies of the main game.