From Lezhin:

Gayoon decides to enroll into a high school far away from home just to be closer to Soha, her middle school heroine and idol. Gayoon finds out about Soha's loss and decides to help her by filling the role of Soha's once true friend - Happy, Soha's pet dog.

Official Webcomic
Official English Translation

From Lezhin:
The school's fastest track star, Namsu. An old friend from the past, Hye-Yeon. Everyone's adorable sweetheart, Joy. High-school romance at it's best! The comic that made Pito one of the best in the GL genre.