Gakuen no Madonna no Watanabe-san ga, Naze ka Maishuu Yotei wo Kiitekuru @COMIC

Story

Ryoichi Aikawa, an ordinary high school boy who’s crazy about fishing, helps the school’s Madonna, Misa Watanabe, when she’s being bothered by guys trying to pick her up by the seaside. After that, for some reason, Watanabe starts asking about his weekend plans every week and ends up making plans with him. Secretly meeting every weekend, the two slowly at an incredibly slow pace begin to close the distance between them…? A frustratingly sweet seaside romantic comedy featuring a single-minded, love-offensive JK and an unbelievably dense, iron-wall boy!

Synopsis via AniList (English).