Yasashii Kankei

From Bliss:

Separated in childhood, Naoya is reunited with his best friend Tsukasa through his work. Though he is seemingly cold and distant, Tsukasa can't get Naoya off his mind. However, when Tamura, Naoya's co-worker, starts to show signs of affection towards Naoya, Tsukasa's jealousy is spurred. Can love blossom with so many obstacles in its path?

This manga also has a Drama CD