She got a love letter from the guy she secretly cared for. After she read it she knew he felt the same. But now she's another school and can't see him anymore. I feel a pain in my chest.(T^T)
The lyrics are about the reunion of "me," who is still living a whimsical life, and "you," who has abandoned her dreams to become a respectable member of society. And this song was written for Bread & Butter by Matsutoya Yumi.