Trader Argyle (Definitely Human). Merseton Tales, #3

Argyle's particular about how to be human, but rules must be broken to save his favorite town. Of all the towns on Argyle Mim's trading routes, he's always enjoyed visiting Merseton best. The residents understand the unusual, and he can't deny he's far from usual. So when he learns of a cavalry troop bent on destroying his favorite town, Argyle races to warn them and becomes more involved in the town's defense than he'd anticipated.
Fen Pepper never wanted to be a cavalry soldier, but when his brother is forcibly conscripted, he volunteers. He's always protected Cor from people who don't understand him, and he's not about to stop now. A monster-killing obsessed captain leads the cavalry troop, and their target is the little town of Merseton, which might or might not exist. When Cor is injured during a skirmish, Fen stays with him while the rest of the troop flees-abandoning them to a town of monsters.
But all is not what it seems, and Fen finds his prejudices and fears challenged at every turn. Trader Argyle takes Fen under his wing and helps him navigate this odd new world. The cavalry will return-Fen knows their captain well enough for that-endangering the people who rescued him and his brother. While Fen reconsiders the bad information he's been fed all his life and tries not to consider his growing feelings for Argyle, he knows he'll have to choose between questionable loyalty and the truth right in front of him.
This book contains: one cat who knows more than she should, some horrible holy relics, and a number of very angry birds.