SPOILER
Based on the latest chapter (95) I assumed it has something to do with the corruption. It's called "Destruction of the Soul". It basically means a human who falls in love with their contracted demon eventually "shatters".
Everyone forgets about them (except other demons), their existence is erased and they break. They become entirely dependent and eternally bonded to the demon.
Hana keeps saying the word "forever" and "eternity" to Lux. The problem is that what she means is her lifetime, but for Lux, he wants her eternally. The only way that happens outside of making her a demon, which he won't do because he already got in trouble for it once, is the destruction.
Remember, he tried to get away from her once he considered this desire to be ugly. He wanted her to have a normal, human life, apart from him. But, Hana was the one who drug him back, but then again she doesn't know. He still hasn't told her the truth.
I hopped onto frtoon with my translator app.
Pass tells her in the next chapter. She doesn't believe it at first until she tries to call a friend and she doesn't know who she is. She then runs into the guy who was interested in her before and he doesn't know who she is.
So, yeah. What you saw was her confronting him. She then makes her wish for him to disappear and never come near her again.
And season 3 ends with Caligo with a massive boner. #-.-)
I cannot.. the raws