Henry & the Dragon by Parker Williams

Henry Cabot is stuck between a rock and a hard place.

When he was a child his beloved sister became deathly ill. The family could not afford her medicine and the alchemist in the apothecary would not help them.
Unless they gave him Henry.
His parents protested but Henry agreed. Anything to save his sister.
For two and twenty years, he’s toiled under Neron’s cruel yoke. He’s also experimented in secret, trying to create medicines for the townspeople.
Neron discovers what Henry has been doing, and sets him an arduous and dangerous task—to collect plants in the dark forest. Except Henry feels certain this task will end with his own death.
In the woods he meets Kai, a traveler who is impressed by Henry’s gentleness and kindness. It’s the first time he’s witnessed it among the people here, and it speaks to him.
The two come to realize that they’re meant for each other.
Then Henry’s master ambushes Kai and attempts to murder him.
That’s when the dragon rises from the darkness.