Dunno how I feel about this chapter. Yeah, it's all cute, but on her side, pretending to throw out something that clearly has sentimental value is just a shitty thing to do, even if it's a prank. And on his side, I feel kind of weird with him proposing to her without actually divulging the fact that he's a demon.
Secrets make for easy drama so I get why the author isn't just easily revealing+resolving it, but man if you truly trust her so much as to enslave yourself to her, you should probably let her know the truth.