I wouldn't call this BDSM dynamic, it's very mild, and they haven't established a pattern yet, this could be a one time thing. But sure nanjo is supposedly a good person, but he went through a lot from being forced, co-erced and then exposed and so on, that messes a person up,
While I do not excuse Mokyeon in any shape or form .
It seems like Nanjo was very successful at establishing distance between him and Mokyeon ,
While Mokyeon needs to be held accountable for what he has done ,him being taken advantage off in a emotionally vulnerable state is not part of that .
Mokyeon was indeed horrible ,but this qualifies less as a justice and more like exploitation ,which again doesn't align with Nanjo's character .
So my takeout from this sudden development.
Is that Nanjo's in his savior complex is choosing not to abandon Mokyeon after listening to his drunk rant ,but since he still has remaining anger from what happened + at this moment Mokyeon fits the criteria of a pitiful person (though he still perceives him as manipulative) + attraction in the mix ,it is translating to him developing sadistic tendencies towards Mokyeon .
But my complain is this ,is while the preference development seems in line with Nanjo ,but on a character level ,it absolutely undermines him as a person ,because while he had a savior complex ,he was also a truly good person .
So him choosing the fact that he already has so much power over Mokeyon and the fact that he is in a very emotionally vulnerable place and willing to do anything because he is tormented by fear of abandonment to unleash this new BDSM dynamics is genuinely shitty and feels strangely exploitative and ooc with the good natured Nanjo we knew .
Idk ,it's cool that Mokyeon is into ts ig ,but this could have waited for him to be in a less emotionally defenseless state (this is in no shape or form defending his past horrible actions though)