Kirakira no Hibi

From Moi-xRyu Scanlations: Every morning high-school student Nanami catches sight of this one surfer he secretly begins to admire. Incidentally, however, it is later on a certain day that they reunite in a classroom! Turns out that this one-year-older senpai, named Shuu, is in fact one who, while characteristically mature, is unsociable to the extent that hea€™s even notorious for being someone difficult to approach. Even so, for some reason, Nanami becomes the sole person that he can smile at and laugh with, over and over againa€| As they repeatedly spend more time together after school, by midsummer, Nanami finds himself receiving a kiss near the seaside?! And so, a story of dazzling first love ensues.

source https://readmanga.re/manga/kirakira-no-hibi/