For years, the Kingdom of Dragonia has ruled over the lands, powerful and unrelenting. The main source of their power, male Dragon-Shifters, are beings given to Knights in order to protect the Kingdom. However, unknown to most, beneath the castle is where the female Dragon-Shifters are kept, deemed to be failures or too useless to the Kingdom for much else than their new purpose. These dragons are used to breed new ones, females taken unwillingly by males that belong to the Knights of the Kingdom.
MC is one of these females. Raped again and again to bare new clutches of eggs, she trusts no one. YC is either a Knight or a Male Dragon-Shifter. If he is a Knight, then he is perhaps suspicious of where the female Dragon-Shifters are, and investigates. If he is a Male Dragon-Shifter, then he is perhaps ordered to choose a female to breed with, to continue his long line of powerful weapons.
Note: Dragon-Shifters do have humanoid forms. Whether you wish for the females to bare eggs or have live births is up to you.