A young girl stands on the sand every day singing a tune that brings back memories for her. Nino "Alice" Arisugawa now sings to the sea after experiencing two painful separations as a child. She believes she is obligated by a vow she made to her two childhood companions. One was addressed to Momo Sakaki, her first love, while the other was addressed to Kanade "Yuzu" Yuzuriha, who was writing music for her at the time. Both boys told Nino that if they were ever separated from her, they would find their way back to her through Nino's voice, even though they had never met in person.
It has finally arrived after six arduous years. Momo, Yuzu, and Nino all go to the same high school. But a lot of things in their life have altered over time. While Momo does everything to prevent a reunion with Nino, Yuzu's feelings for Nino, which he most wished to conceal, resurface. This is in contrast to Nino's unrelenting pursuit of fulfilling her childhood promise. Will they be able to overcome the emotional turmoil of their love triangle and restore their old friendship through music?
