Torikago no Tsugai

Torikago no Tsugai (鳥籠ノ番) is a manga written and illustrated by Minami Toutarou. It was serialized in Gangan Online from August 16, 2012 to April 17, 2014

Plot
To search for a missing friend, 6 people arrived in a closed theme park, "Birdcage Castle" which should be deserted. However, in there, groups of two people are created and are connected by a chain, and now, the game of putting one's life on a line began!