Shishunki no Zawazawa

Shirasaka, a high school student, has been feeling anxious and restless lately. His close friend Kuroda, who is better than him in school and sports, suddenly grew taller and more mature-looking, and he feels as though he will be left behind. One day after school when club activities ended, a still-anxious Shirasaka was napping, and was suddenly kissed by Kuroda?!

(Source: Gentosha Comics, translated)