The tatoo artist used rape to scare him off and to show him that although he gives consent, he is only doing it for sensei.
^
I think you lowkey misunderstood what the seme meant. He knew that the uke didn’t want to do it with him but for the sake of the “creation/sensei” he would offer his body to the seme for like I dunno compensation?
Seme realises this and basically says “ok I’ll rape you then” cause he knows it ain’t consensual on the Ukes part. He did it to scare him off and was basically telling him “save it for your significant other and don’t throw your body away so easily”
Plus it probably didn’t sit well with him after hearing “do what you want.... I’ll do anything for sensei”
I dunno that’s how interpreted it :))
Saying you’re going to rape someone and end up not doing it does not make you a nice person. Can authors stop using this trop to show that the character is a “nice” person and therefore the love interest should fall in love with them cause they’re are a “nice” person.