i think konoha rek makes a good point about being a spy thing... if he's a spy, he shouldn't have a seal visible. But does the seal have to be on the neck? Do all 4 of the sound guys have it on their neck?

Also, it should be easily coverable with some genjutsu

another thing, is it that oro is just cheating sasuke and really just wants to take over his body (sharingan)? because oro wants sasuke to be his soul host, stated during his konoha destruction saga. But then now it seems like he has more in stock for Sasuke to do