From Bad Eggs:

Everyday Kenji confesses to Aya. She likes him but she doesn't know how serious he is. One day, a girl from a younger class appears who likes Kenji. What will happen to Kenji and Aya...?

This oneshot is the title story in the volume work "White Carol" (ホワイトキャロル). There 4 other oneshots that are in the volume work.

summary by Divine Sanctuary
Asahi is a 7th grade student who's very bad at sports. She joined the volleyball club when she entered junior high school, only to quit it one month later because she couldn't keep up with practice. Feeling discouraged from all kinds of sports, Asahi was reluctent to join the badminton club, will she just be the laughing stock of the class again, or will she find some new hidden talent? Read on to find out!