The story centers around two musicians and lovers, cellist Aika and pianist Takaya, who share a dream of one day moving the world with their music. Takaya devotes himself to composing pieces while doing part-time jobs, and Aika watches over him. But one day, after composing the "Angel Sign" piano-cello duet piece, Takaya suddenly he passed away because of heart attack. Aika continues to play the piece alone, and eventually, the piece will spread throughout the world. And their music brings various miracles in the world.