Fragments Blue

One summer day, a young man named Kaname Ōsaka receives a letter with no return address. "If you remember where I fell, go there with Momoka and search." The letter includes a small key, and is signed by Chika Yazawa, Kaname's childhood friend and Momoka's sister. However, Chika had died two years earlier when no donor could be found for a heart transplant. Kaname and Momoka, along with their friend Natsune, have no idea what the letter means, but decide they must investigate. Fragments Blue is ...