Gakuran no Naka made Sawatte Hoshii: Sono Saki

Niimi and Sawane met in the student council of a boys' school and became lovers. After graduating from high school, the two high school boys choose different career paths, and they don't see each other for a long time, but then summer vacation arrives...!

(Source: Shogakukan, translated)

Note: Includes two extra chapters.