Seikishi desu ga, Takane no San Seijo no Dareka o Yotta Ikioi de Daiteshimatta Ken ni Tsuite

Blade endures harsh training alongside rivals and three elite saint candidates to become his dream role: a Holy Knight. But one absolute rule governs these knights: they must only bond with a partner officially recognized by the Church. Violating this means ability confiscation and expulsion. One morning, Blade awakens to find a Sacred Mark—proof of an unrecognized bond—carved onto his lower torso. Now he must find his secret partner while guarding the mark's existence... or face ruin!