Regatta: Kimi to Ita Eien (2002)

Blurb:
High school senior Herman is out to prove to his old teammates that he’s responsible enough to lead a rowing crew to victory in this year’s eagerly anticipated inter-school regatta. However, Herman’s attraction to hunky teammate Mar may throw his well-laid plans out the window. And it doesn’t help that Mar is in a relationship with his best friend’s sister. Can Herman keep his feelings in check until after the regatta? Or will this doom his crew before they even get a chance to hit the water?

Source: www.anisearch.com/manga/3360