Mono was locked up in this four corners of the signal tower for many years..he lost count to 10 years and he felt helpless already, after getting betrayed by his trusted friend and leaving him in this lonely place.

He realizes that he was powerful and have same ability as the once he fought.."the thin man", mono was not sure if this is coincidence or not

The door with a curved eye opened.. He look blankly to it, there have a small hope lingering to him that he was free again

Mono didn't expect who opened that door...