Mutten Kylegate is a major character in On the Way to a Smile: Case of Shinra. Kylegate is described as a man in his thirties wearing a worn navy blue army jacket with a sturdy build. Kylegate is a former lieutenant in the Shinra army and was born into a rich family. According to Veld, because of his wealth Mutten was never required to serve in the army, but chose to anyway. He came under heavy criticism for his actions, including excessive brutality and torture, and thus was never promoted beyond lieutenant.

Kylegate invades Rufus's refuge in Kalm with a mob and takes him prisoner in his mansion. Over time, Rufus reveals his plans for a new city on the outskirts of Midgar, and gives him passcodes to Shinra warehouses for supplies. Kylegate gathers people to begin construction of the city, telling Rufus he intends to govern it himself. However, shortly after telling this to Rufus, Kylegate is shot by one of his subordinates, and Rufus is subsequently rescued by Kilmister.