Kazuya Aoike successfully catches his tenth cuttlefish, while Tsukasa Domyoji has not yet caught any. Tsukasa does catch an octopus, amusing Kazuya as it spits ink at Tsukasa. The two argue for a bit, before Kazuya says "It's your fault that Tsukushi's changed!" After Kazuya finishes his story about Tsukushi, Tsukasa correctly guesses Kazuya's feelings for her. Tsukasa then arrogantly boasts, "She's in love with me!", telling Kazuya he has no chance.
Meanwhile, Tsukushi Makino, who just heard Rui Hanazawa confess his feelings to Shizuka Todo, has collapsed from shock. She eventually comes to terms with her own feelings for Rui, realizing he was always the person she always wanted to see. As she starts to cry, Kazuya and Tsukasa return from fishing. They invite Tsukushi to eat the cuttlefish with them. Tsukushi is distracted from her troubles by their banter, saying to herself "I'm not alone tonight." She then offers to help them cook the fish.
Rui and Shizuka are still kissing, when he suddenly stops. He asks her why she is being "placid" since he forced her into the room. She replies, "We're a man and a woman. This was meant to be." Tsukasa then bursts into the room and invites them to eat. On deck, Tsukushi offers some fish to Rui and reveals that she saw him with Shizuka. After Rui bluntly replies to her question, Tsukushi says "Please don't hate me", to which Rui says that he does not. Tsukushi looks around and silently thanks Tsukasa for distracting her.
Chapter thirteen was first released with a one-page color illustration, featuring Tsukushi wearing a wide-brimmed hat. The image was also included in the art book and volume two of the complete edition.