Natsu to Mushikago

"Keep winning and we'll be able to see each other at nationals!" In order to keep his promise with the girl next door who moved away, Keiki aims to be a basketball champion! But he quickly quits after getting his butt handed to him by a real basketball prodigy. As the seasons pass and his wounds heal, Keiki is once again drawn to basketball by an unlikely new arrival.

(Source: MANGA Plus)