After the breakup of his middle school swim team, Ikuya decided to get stronger on his own and not rely on anyone. But then Haruka, breaking out of his freestyle comfort zone to swim in the individual medley, tells Ikuya, "You're not alone." As the two race side by side, Ikuya hears the sound of Haruka swimming, and suddenly he feels something in him changing...
Haru-chan's challenge 
against the world begins!
!يبدأ تحدّي هارو-تشان للعالم
Haru-chan fordert
nun endlich die Welt heraus!
Empieza el reto
de Haru-chan con el mundo.
Empieza el reto
de Haru-chan con el mundo.
Haru va bientôt défier le monde !
La sfida contro il mondo di Haru-chan ha inizio!
O desafio do Haru-chan
contra o mundo começou!
Харусик бросает вызов миру!