Hatsukoi made no Shouten Kyori

Haruto, a university student, has been harboring a one-sided love for his childhood friend Tsubasa. Tsubasa, a popular guy admired by girls and working as a fashion model, has always prioritized Haruto above anyone else. But now, their time together might be running out... In just six months, Tsubasa will be leaving the dorm to live on his own. Feeling increasingly lonely, Haruto ends up talking to Tsubasa about a confession he received from a junior student...

(Source: Tokuma Shoten, translated)

Note: Includes one extra chapter.