Inside of the game, Sonic Mania. Tails and "Sonic" were going through the chemical plant zone while trying to avoid the chemical flooding. While escaping the flood, Tails was tripped and grabbed on the ledge and he need "Sonic's" help."

Tails:"Sonic help!"

"Sonic" came here to Tails and looked at Tails before smiling, his eyes turning black and he said this

"Foolish fox, You should've known it was me"

He kicks tails off the ledge and watches him dissolves in the chemical before he teleported back to green hill zone