Just because the guy is into getting NTR doesn't make it any less NTR
I thought NTR was when the person getting cucked was not aware or was against it. If the person was aware and enjoyed it, should just be cuckolding and not NTR.
NTR, netorare, passive form of netoru, literaly (protagonist) has their (girl|boy)-friend pinched, is when one or more relationship unrelated person(s) has/have sex with the protagonist's significant other and protagonists cant do shit about it
and the SO remains with the unrelated person(s). Everything else is sharing, swinging, groupsex, prostitution or other porn tropes despite the whiner's crying.
NTR, netori, is the active form of netoru, literaly the protagnist steals the significant other.
There is significant overlap with BDSM as netorare stories are specificaly addressing an audience wanting to get hurt and tortured (subs), netori addressing audiences wanting to hurt and torture (doms/tops). Force multiplying parameters are when the target is unwilling (at first), events happen before the first sex in the relationship and virginity. Additional reinforcement comes from being forced to watch either tied up, by recordings, remote connection, stunned, paralyzed, etc as well as degradation by insulting or appealing to the inferiority of the target towards their former partner before ultimately breaking up with them.