Btw, those confused about the MC appearing in the mother's dream, in Asian culture, it's not unusual for the spirit of the deceased, especially family members, to appear in dreams providing information and stuff. So I'd imagine the original spirit of the body gave a message to the MC and when that didn't work, appeared in his mother's dream to say that the brother is trouble. If it's something to do with the wellbeing of one's family member, then its usually taken seriously.
so with that, the MC knows it's not just a nightmare but instead a message and confirmation he needs to go.
Thanks for the translation! Appreciate the hardwork!!