Kuro no Kishi

Black Knight, the highest honor that can be bestowed upon a knight in the kingdom of Aran. Sieg O'Brian may have his eyes on the title of Black Knight but he's also after another prize, the young prince, Chris. Black Knight is a sweeping romantic fantasy epic about the relationship between the prince of a medieval kingdom and his loyal guardsman. Our story begins when Chris and Sieg meet in military school and embark on a life-long relationship fraught with danger, treachery, and above all, love.

(Source: BLU Manga)

Kuro no Kishi had four volumes published in English as Black Knight by Tokyopop's Blu Manga imprint from July 3, 2006 to February 3, 2009 before the publisher went defunct.