Kyou, Koshiba Aoi ni Aetara.

Sahoko had lots of friends in high school, so there’s no shortage of people to catch up with at her reunion. But the one face she wants to see is missing: that of Aoi Koshiba, her classmate and first love. A star of the basketball team, Aoi caught Sahoko’s eye as an easy way to score social points. But when Aoi quits the team, an unexpected kiss pulls Sahoko closer to her than she intended to be. With a difficult home situation, Aoi is in need of more than just a cynical social climber. She needs a true friend, and something more…

(Source: Kodansha USA)

Note: Chapter count includes Chapter 0.