So far there are 4 Tag-named characters. I recognize 4 out of 5.

So who is the the girl to the far right (beside Rin Natsume)? She looks like Makoto from Kanon but I could be wrong. It is usually one [Key] girl per story when it comes to cross-over arts like this.

That's the new girl from Rewrite. Apparently her name is Chihaya Ootori.

Oh thanks Juhachi. I'm gonna do a little study on her.