this is how most people see it. I think.
Netorare - your partner is stolen. (usually through SA or blackmail)
Netori - you steal someone else's partner. (You choose your own methods. Or your stealing from an abusive relationship.)
Netorase - your partner is shared. (usually with dubious consent)
BSS / I liked her first - no established relationship. Someone confesses before you.
Cheating - Your partner knows exactly what they are doing. Or you are two timing.
No this is not how most people see it if you mean your crush being stolen. That is more friendzone territory then NTR. There is only a handful who do. It only becomes NTR if you are in a relationship. Also NTR can happen without SA or blackmail easily, it basically is cheating while they steal the partner. This can happen through many ways.
(edit) Basically if this was the case it means if you have a crush IRL, but she starts dating some1 else and she friendzones you that already is NTR by that logic. Which means NTR wud be fairly common.
Actually some people don't, this is the only reason why we had to classify it NTR, take that away and the game has no NTR, which imo it doesn't have.
I guess by your comment you never been on f95zone yet. We have had multiple comments about it.
There even were comments on the current love dolls being NTR even if you don't know most of them.
Go tell the developers like N_Taii that their games aren't NTR, they'll laugh at you. Games like Scars of Summer? Not actually NTR according to guy that self-admittedly doesn't like the tag and probably doesn't engage with it.
Don't just google the word, you'll get a literal "definition" that is removed from the tag. For better or worse, this type of content is a staple of NTR as a genre. Your real life example ignores context like the depiction.
