Yu Narukami

Yu Narukami is a major character in Season 4 and Season 5.

Season 4
In Chapter 1, Yu awakens in the Jungian facility, and meets Aigis, Ren Amamiya, and Ann Takamaki. Yu then encounters Tohru Adachi, who he thought was arrested. The killing game was then announced, and he quickly befriended both Aigis and Ren. Kazuichi Souda was then murdered by Ann Takamaki, resulting in Yu inadvertently killing Ren due to Ecto wanting Luna to suffer. He then attempted to choke Adachi, who had laughed at his death, to stop due to him not wanting to stoop to his level. He then later found Amamiya revived, alongside Aigis.

In Season 4, Yu Narukami was admined by @insoxmina

Season 5
One year before the events of Season 5, there was another killing game. Yu was one of it's participants, and was the sole survivor after an incorrect vote on the mastermind(s). Tohru Adachi revealed himself as the "sole" mastermind, and slaughtered the remaining cast besides Yu, who escaped into the fog, where he had been residing inside Konishi Liquor until Season 5.

In Chapters 1 and 2, the real Yu Narukami was left unmentioned.

In Chapter 3, the motive allowed people outside. There, Amamiya encountered him, and he first learned of his own shadow's existence, and his assistance to running the killing game, due to how Amamiya had accidentally mistaken him for it at first. He was then brought food, and quickly befriended Amamiya.

[Note: Here on out, these interactions may not be in order, and will not have chapter tags due to not remembering when these occurred.]

In Season 5, Yu Narukami was admined by @despairing.naegi

Trivia

 * In Season 4, Yu Narukami was the only cast member to have never died once throughout the entire season.
 * Yu Narukami was initially deceased during the events of Season 5. This was later changed.