
If you are talking about Red Death he’s a man. I believe it’s shown he’s the MC’s older sister’s boss. But, I think you maybe are getting them confused with the evil lord leader of the Chinese group invading right now. In which case, in one of the editors notes they explain the gender is being purposefully kept unknown and only gender neutral language in the original Korean has been used so we literally don’t know at this point as it is intentionally being kept a mystery

Omg noooooo, Red Death is the lady shown in the last chapter. Can't you tell how she talked about Mujin as a peony to be acquired when she rejected her offer. It was because Red death was the reason for her father's death. Red death is the leader of the Chinese villain troupe. Coz her subordinates are so so powerful they can counter the top psykers

You're talking about the guy that took interest to Cassian's sister right? That is the head of the US Psykers, it actually mentioned that the order to protect Cassian (His current body, can't remember his Korean name) is from the head of the US Psykers. Now we don't really know if the head is involved on killing Jeff and Cassian but from the looks of how the others (that involves on killing Cassian) that seems about right.... Would've been odds if he didn't know about that and/or the others (that scheme and kill Jeff and Cassian) acts so "respectful" toward him, even if he is the head, it seems there's more to it.
But then again it is just a theory

The sister see the big boss? Eh? When? I just remembered the Psykers that kill Jeff, kneeling over the sister's boss, yes the guy that is in the picture with Jeff, but after Cassian's student got the mission that I realized that guy is the US Psykers head. At first I also scratch him off as one of the killer (we only don't know one more person) but then again, most of the Psykers that kil Jeff was his friends too, I feel like if he's betrayed by his closest one that would make sense BUT like I say, it just a theory, and I might've been overthinking of the picture as a misdirect so we don't get suspicious of the guy LOL but anyway I digress, it could be also a mistranslation because when I reread again, he's def the head of the US Psykers
yall is red death a man or a woman. pls im so confused atp