There's elements of NTR with Isabella considering we don't know what happened to her husband. You are technically cucking him IF he shows back up.
Other than that I don't think Elena counts as NTR cause JB seems into it? Like he's not jealous and it's not behind his back or anything. She's not cheating on him cause she'll go back after you do anything. They're just swingers which isn't NTR.
Edit: I'm not even sure Isabella counts as NTR though because she has a lot of regret and takes a lot of (weird and kinda rapey) effort on MC's part to even see her titties on purpose.
Other than that I don't think Elena counts as NTR cause JB seems into it? Like he's not jealous and it's not behind his back or anything. She's not cheating on him cause she'll go back after you do anything. They're just swingers which isn't NTR.
Edit: I'm not even sure Isabella counts as NTR though because she has a lot of regret and takes a lot of (weird and kinda rapey) effort on MC's part to even see her titties on purpose.