If Doha is indeed a player to begin with, why can he kill the Murderer NPC but not Bada? If he's an NPC it could explain why he can affect other NPCs cause he's part of the game world, then he became an NPC turned player later. (1)
for the others if they are also initially players, then Jae-Seob and Bae Hyungshin that have the soon-to-be lovers trope and seems to have their feelings for each other wired into their character design as seen when BH tried to caution/prevents the other and SB killing Bada & Doha when BH died; its too much of a coincidence if they are also lovers in real life (1)
there is also the possibility that Doha has an attribute trait that enables him to cause real damage to NPCs because of his personality (? designated character) while Bada's trait/character design could be a quick to notice but silent know it all or the information gatherer; more intelligence or something similar but has a "not enough strength to kill" or "cannot kill people" attribute (2)
If Doha is indeed a player to begin with, why can he kill the Murderer NPC but not Bada? If he's an NPC it could explain why he can affect other NPCs cause he's part of the game world, then he became an NPC turned player later. (1)
for the others if they are also initially players, then Jae-Seob and Bae Hyungshin that have the soon-to-be lovers trope and seems to have their feelings for each other wired into their character design as seen when BH tried to caution/prevents the other and SB killing Bada & Doha when BH died; its too much of a coincidence if they are also lovers in real life (1)
there is also the possibility that Doha has an attribute trait that enables him to cause real damage to NPCs because of his personality (? designated character) while Bada's trait/character design could be a quick to notice but silent know it all or the information gatherer; more intelligence or something similar but has a "not enough strength to kill" or "cannot kill people" attribute (2)