Rika-san, Kekkon shite Kudasai!

Synopsis

Kotaro Wakayama is a high school boy who gets a lot of attention from girls for his cute looks. However, he has never had a girlfriend, which may seem strange to other people. In fact, there is a reason for this. The reason is that Kotaro is still in love with Rika, the older girl next door whom he had a crush on ever since he was a child. He even plans to "marry" her! Will his timeless love ever reach Rika? (Source: Kadokawa, translated)