Dansou no Partner

Mitsuru Masamune, a mild mannered high-schooler who hasn't had much of a presence since his birth one day had a roommate move in. A silver-haired, blue eyed exchange student all the way from Germany, Leo. They had a dignified appearance and had a cool way with their words with no room for timidity. He used to think that Leo was a being far off from someone like him till he got to know about a secret of his after which their relation got a bit more special...?!

(Source: Square Enix, translated)