Sea Cat Scramble.Yuto, Himari, and Rinko are invited by their class representative for a trip to the beach as a welcome to Himari. While walking home from school, Yuto reluctantly agrees to take Himari swimsuit shopping, and Himari goes on ahead of him. While calling Rinko, it starts to rain heavily, forcing Yuto to take shelter under a bridge where Shizuku appears and warns that she will kill him if he goes on with his Demon Slayer heritage, vanishing with the rain clearing up. Rinko joins Yuto and Himari at the department store, where Rinko helps Himari decide on a swim suit and Yuto chooses a Western-style dress for her. At the beach, it is revealed that Himari is afraid of water, and Rinko throws her an inflatable whale toy to float on. While the others are having fun, Himari, having drifted far from the shore, gets a startling visit from Yuto when a giant wave appears from behind and crashes onto them. Both of them survive but are dragged down into the ocean by a set of tentacles. After regaining consciousness, Yuto meets Shizuku, who warns him that his awakening as a Demon Slayer will destroy the balance between humans and ayakashi. Just when she is about to kill him, Himari intervenes but a second mizuchi appears and restrains her. Shizuku conjures up a whirlpool to drown her. Yuto quickly jumps into the whirlpool and attempts to rescue her. Himari saves him by stabbing her thigh with one of Shizuku's ice spikes, causing the whirlpool to disintegrate from her blood, and destroys the second mizuchi. Himari tells Yuto to run while she holds Shizuku off despite her injury but Yuto refuses, telling her not to sacrifice herself for his sake. Deducing there is something unusual about them, Shizuku withdraws from the battle, but not before telling them that she will kill them next time.