that's not how it works .. they only feel each other's pain not physical sensations so ml wouldn't actually feel his own dick up his ass unless he shoved it in & made it painful. also the severity of the pain isn't the same so if minchan gets stabbed in his stomach with a knife the ml would only feel like a tingle in his stomach or a less severe stomach ache not the feeling of a knife in his stomach this is all explained in the creators note
wait really?? which one? i was binge-read this from chapter 1 so i didn't read any creators note.. but still! his dick is big enough and i bet minchan kinda feel hurt too before getting ecstasy. and also you said it hurt are less for bihwan so you mean when he fucked minchan, bihwan's ass getting tickled??!
Your exact question is answered in bonus: Special Episode 1. In ch15 Bihwan tells Minchan: "Even if I do it so rough that I end up crushing your tender organs, both of us will feel the pain" so I imagine unless he went out of his way to hurt him until he's tearing down and bleeding there won't be any sensations. On a serious note though why are you hyper focused on whether Bihwan's ass will be tickled or feel tingly lol
yeah sorry about that my imagination is too wild about " if he feels something then the others did too!" and ignore all the special note that author already explain. or maybe im reading too much forced seggs bl nowadays so my mind already autopilot thinking the uke's butt will always gonna be hurt and you know how it goes. and ngl its kinda funny tho about tickling butt when they had seggs sorry again

sooo they can feeling hurt to each other. does that mean.... they can feel each others dick to each others ass?? minchan might be used to it but what about bihwan(is that ml name right?)? lmao is this more like how fuck-self feels like, and sure some dokaebi already feels addicted because he can lowkey can feels his own dick to his ass probing open