I think the reason why they're an asshole to Yugeon from the very start was because they expect him to die just like any other guide that died from the previous mission. They themselves don't look at their selves as human anymore and instead as monsters. All of them think their awakening was a curse since they had to suffer so much by losing so much (loved ones and everything else) and no one treat them as human anymore but as tools. Maybe along the journey, they forgot how it feels to be human that's why they didn't treat Yugeon as human at all and just sees him as a tool. And I guess, seeing how Yugeon grieve for his brother and act with everyone else, they realized that he still is human after all, capable of feeling emotions. Which I feel like also made them realize that they were once a human before awakening and maybe that's where their concern came from.
i know and could guess as much. it's just a sarcastic remark given to what they all did regardless their view and reasoning. nothing too deep
woah that's some character development there like bare minimum lol. them showing concern and all are we near the ending? i feel like i may have to reread this all over again once it's finished to understand everything