Iori spends her holidays working as an actress, shooting a movie at the waterside of a lake, which has a mysterious small island called Lover's Island at its center. Ichitaka, on a biking trip, coincidentally makes a stop at the location where Iori is shooting. Meanwhile, Itsuki returned from her job as a molding artist in the United States and plans to meet her childhood friend Yosuke to fulfill a promise they made ten years ago. Walking along the railroad track she, Yosuke and Ichitaka went along ten years ago, Itsuki is confused when she sees the lake with the small island in it at one side of the track, as she does not remember there being a lake. Yosuke, along with three of his biker friends, is also on his way to meet with Itsuki. However, the other bikers reveal to him that they are planning to rape Itsuki. He drives ahead to save Itsuki from them, but drops from his motorbike just as he crosses her path. The other bikers close in on him, stab him and let him drop into the lake (which he can not remember being there when he was a child). As the bikers spot Itsuki, she runs away.
Iori pasa sus vacaciones trabajando como actriz, filmando una película en la orilla de un lago, que tiene una misteriosa pequeña isla llamada Lover's Island en el centro. Ichitaka, en un viaje en bicicleta, casualmente hace una parada en el lugar donde Iori está disparando. Mientras tanto, Itsuki regresó de su trabajo como artista de moldeo en los Estados Unidos y planea reunirse con su amigo de la infancia, Yosuke, para cumplir una promesa que hicieron hace diez años.
アイドル路線を拒否して女優として歩み始めた葦月伊織。造形家を目指し再び渡米した幼馴染みの秋葉いつき。その２人の間で揺れる思いを抱いたままあてもなく独り自転車ツーリングに出た瀬戸一貴。
それぞれの目標に向かう３人のひと夏に起こったもう１つの「I"s（アイズ）」の物語です。
