Still in the Light

(from ebookjapan):

Shizuka Koike, a transfer student, is a bright and energetic girl. On her way to deliver newspapers, Shizuka meets Momokai, who lives in a large mansion, and is happy to be in the same class with her.

Shizuka learns that Momokai has a younger brother named Yukio, but both Momokai and her mother insist that Momokai is their only daughter and has no younger brother. One day, Shizuka goes to Momokai's house to visit him and learns a shocking truth about Yukio...

In addition to " The Morning Sun is Yonder" the collection also includes "Still in the Light", "Tanabata", "13 Candles", and "My Christmas".