The Bone Collector by Onley James

Park Chen has spent most of his life as a killer—a deadly, deep cover operative known as the Bone Collector. Now, he’s been benched. Reassigned as an instructor at Project Watchtower, he’s tasked with training a school of psychopathic assassins while trying to keep a promise to his friends.

Gift Ayutthaya isn’t treated like a gift at all. If anything, his parents treat him as a burden, though a spoiled one. After an attempt on his life, they pass that burden onto someone else. Park. The man Gift’s been fantasizing about for years. A man who sees him as an adorable but incompetent distraction.
It’s no secret that Gift doesn’t belong at the Watch, but Park’s made a vow to keep him safe. Gift has made a vow, too. He’s going to use every weapon in his arsenal to find a way to seduce Park and make him love him, once and for all. Or die trying.

Loving Gift was never the issue—Park’s already there. But assignments at the Watch aren’t optional. To stay, Gift has to prove himself, something Park just can’t allow. Can Gift get Park to see that, when it comes to murder, Gift is aptly named? Or will he be relegated to the sidelines in both school and in love?