Thank you so much, I'm happy you enjoyed my game!
[vague spoilers below]
The lighter unlocks the little scene at the end where Cedie lights the candles on the desk, otherwise she would skip that and go straight to bed. The game is kind of unintuitive by design so there are a few details and scenes that players won't see unless they interact with certain items at certain times, etc. There's a specific one that I would be a bit surprised if somebody found it on their own.