Kei Shinomiya (紫宮 京, Shinomiya Kei) is a High School 1st Year student from Group K.

He was originally from the regular games, participating as the "Seeker" in the second game, Friendship Hide-And-Seek. He and Banri was also in charge of finding a place for Juuzou to hide. He later makes his debut in the first Adult Tomodachi Games, "Prison Game of Friendship", as "Prisoner Number 001".

He sometimes calls his childhood friend and neighbour, Banri Niwa, "Big Brother".