Shu works at a pizza restaurant. When he is on his way to deliver, he sees Nagi, who wants to be a voice actress, practicing at a riverside. When he is on his way back to the restaurant, he sees Nagi again but they get involved in a truck accident and lose their lives...

They come to a school located between this world and that world called "Conservatory". They wake up and find out the fact that there is a way to go back to this world. It is necessary to win a music contest done one-on-one. This means a winner can go back and a loser can't. Ironically, Shu is going to have a one-on-one match against Nagi, who is actually tone-deaf... Shu suggests that they practice together until the contest day...

[From Himeya Shop]

Beside the adventure parts that makes most of the game, Dear Pianissimo includes musical sequences. In which the player is required to press keys on the keyboard in correct timing to accompany the current song. These sequences can be turned to automatic if the player doesn't wish to participate.