Shounen Ga Otona Ni Natta Natsu - 01 🎯 High Speed

A slow, humid summer morning. Cicadas crying in the distance. A boy on the verge of adulthood wakes up to find the world hasn't changed — but he has.

No huge drama yet. Just a boy (15? 16?) spending the first week of summer break realizing his friends are moving on — one got a summer job, one is studying for exams, one is dating. He feels left behind. Episode ends with him taking a random bus to the coast. shounen ga otona ni natta natsu - 01

As for the anime adaptation, I couldn't find any information on a direct anime adaptation. However, there might be live-action adaptations or other related content. A slow, humid summer morning