Responses
This is just my guess but I think both of them did not hide their feelings anymore. Muheon know Seungju likes him, and Seungju knows Muheon is flirting with him. The problem is that, they probably think that their relationship cannot go further:
1) probably because of their families
2) because they've been together since childhood, so its awkward
3) the more they get intimate, the more Seungju being exposed to danger since he is an empty vessel (this is my strongest opinion)
I getting pissed off with this MC. You know what you want from him and what you feel about him. Just ask him out ugh. I'm feeling frustrated here.