I'd say only him and Shadow are actually aware of it, I mean, Sonic knows but acts like he doesn't, or at least doesn't put thought into it... up until he did, but then Nine had already drawn his conclusion, so it was kinda late. I must know how it ends!! D:

It makes sense, he was already casted away from his society, then this guy becomes all buddy buddy with him hardcore and leads him on a quest where he could fix everything wrong with his life, start anew. Only to say "yea, after this you stop existing and I get my home back". I'd be annoyed too xp