The 'Chains' part being about how a demon is kept in check by a young, weak human. The human happens to be the chains that keep the demon from going beserk or something.
The 'Choices' bit varies on the actual plot. Which I can't decide on. All I know is that the demon will do everything in its power to protect the human.
I'm fine with whatever time period you'd prefer. Another idea could be that if it's an older time period the human is being forced to marry? Like an arranged marriage.
Hehehehe, I'm feeliong evil just thinking about it. How about a.....noble's daughter........who met the demon when she tried to convince it to stop harrassing some defenseless villagers. The demon agreed to in exchange for the daughter. Now it basically just follows the daughter everywhere and stuff.