i think he’s this stereotypical aspd model who thrives on deceit and hurting other people to get his way and internal pleasure. he reads people well, and once he made megumi fall head over heels with him—over time, slow sweet and gentle—he then uses that attachment to get way more “fun” than your typical soap opera romance. cheating would be another stage of the development—just seeing megumi all worried and anxious over him coming back home way too late, face locking his phone apps, smelling somewhat different than his usual cologne, just to slowly make him discover the hidden “romance” sukuna couldn’t care less about, see him in shambles, crying, begging sukuna to stay… that’d be surely a pleasure greater than sex for an individual like him