Hoshiiro GirlDrop Comic Anthology

Daichi Taira and Sosogu Hoshifuri were as close as anyone could get as children. Together, they made a promise that when they got older, they would live together and get married. But Sosogu moved far away one day, and he never saw her again. A couple of years later, Daichi is a regular teen living a humdrum life. Not even his parents leaving for an overseas trip can change that. Just before the pair can get out the door, his mother gives him a bit of advice among the usual warnings: "Take care of Sosogu". Unfortunately, he cannot exactly remember who or what Sosogu is...

(Source: MU)