It’s not that he has some perverted thoughts, when they awaken for the first time, they have like so much energy in their body that they must release them as soon as possible, so he doesn’t remember his sister anymore and only thinks about releasing his power/pain.
Awakeners, esp high level one, are in constant pain so having a Guide can ease their mind and body, just like a drug.
His sister was a guide, and he just awaken and can’t control his powers. He was relieved that a guide was with him and wanting more… but the sister was just a kindergartener? I forgot the novel. But yeah her sister can’t manage his powers since she’s still small so she melted.
I think he can't completely control his power yet so he drained and melted her.
Thanks guys. I didn’t think about how she was probably involuntary guiding him. Sad
Why did he have that creepy relieved face when he did it? Did he have a sister complex or something?