While the Iwatobi High School and Samezuka Academy swim teams plan a surprise going-away party for Rin, who is leaving for Australia soon, Rin sees Gou and Momotaro together and assumes they are dating. He discovers that Momotaro plans to challenge him to a relay along with his older brother, Seijuro Mikoshiba, making him even more concerned about losing Gou. When Rin enlists Haruka for help, he reveals that Momotaro had wanted a toy Rin had gotten at a burger restaurant. Nevertheless, the two race against the Mikoshiba brothers. After winning the relay, the swim clubs celebrate Rin's departure. Meanwhile, Ikuya Kirishima and Hiyori Tono prepare for the upcoming time trials at their college.