Wrong information let me correct spoiler -
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Uncle is actually can't get hard but he brings bunch of young boys and make his soldiers rape them in front of his eyes sit there and only touch them and seme is one of them who also does that , after he brings uke they did same seme and other soldiers rape uke in front of uncle and they even recorded that which later prince sees , also we will be seeing sex between uke and prince only good part about their sex is uke is consensual and prince was very gentle with him it was Total love making unlike sex between seme and uke but he did 5 times with uke (cuz he is young lol) , atp seme start to get jealous of how uke start ri relay emotionally with Prince than him he can feel uke getting taken by Prince good side which kinda made gim aware of uke words and let gim affected him ... Later on they prince and seme become love rivals cuz seme get caught him prince that he is kissing uke and uke was pretending to be good person but he also feel prince is innocent in it guilty about it so seme said "i love ryujin but he doesn't love me it's one sided"... That was actually funny to see seme getting jealous though as if he didn't put two young people together they get more closer to each than seme old community dick

I've read how in the future the prince's uncle rapes the ML, along with his subordinates and Haebum as well. What I don't see is if anything happens between him and the prince. It's obvious that the prince is somewhat smitten with him, I'm wondering if he acts on that or if Ryujin, at least, escapes that trauma.