This is Ookami Wolf, she was Tails lover for 4 years. She was killed by Niles because that she was Tails' weakness. But after Niles kills Ookami, he tried to kill Tails but fails and Tails escapes  with a big scar on his upper chest. Luckly he survived but he is still sad that Ookami is gone and has no one to occupy him like she did.