These Silent Stars by Chani Lynn Feener

The Devils of Vitality always spot a liar.
Rin Varun’s got something to hide.
That’s a lie. He’s got several things. Traveling to a different galaxy was meant to make his life less complicated, but a year in on this new planet and he’s still fighting off his demons. There’s no better place to learn how to keep skeletons buried than the Academy, where they teach their cadets how to uncover them, and Rin is determined to graduate in order to ensure those demons stay hidden. He doesn’t want to stand out, doesn’t want accolades, or high marks. He just wants to coast by unnoticed, and he’s doing a decent job until he draws the attention of the Devil Prince.
Kelevra Diar doesn’t do disguises.
Who would bother with a mask when they have a face as tantalizing as his? As the Imperial Prince Third in line for the throne, Kel’s used to getting anything and everything he wants faster than he can raise his hand to snap his fingers. The drawback to this is even murder has lost its intrigue, and there’s nothing more dangerous than a bored Devil of Vitality. Then a cadet catches his eye and suddenly things are starting to look interesting again. Rin is unlike anyone Kelevra’s ever known, with monsters hiding under his bed that might rival Kel’s sociopathic nature.
When Kelevra decides to make it his mission to draw those monsters out to play, Rin unsurprisingly resists, but that only makes him more invested. Suddenly the impulsive prince realizes he’s in this for the long haul, even if that means forcing Rin’s hand through an arranged betrothal. Rin has no idea why Kel has taken such an intense interest in him, but no matter what he tries, he can’t shake free of him. The sex between them may be explosive, and Kelevra may be the most attractive person he’s ever seen, but is that enough for Rin to drop his guard and reveal all his secrets?