sigma (fate/strange fake)
The son of Hisau Maiya, After she got raped by a soldier and gave birth she had to abandon her child. He was then taken in by the government and given the name Sigma and was briefly mentioned in Fate/Zero.
In his debut in Fate/Strange Fake he was originally supposed to summon True Lancer but to his surprised, he summoned Watcher_(Fate/strange fake) instead who was an entity created by the gods.
He becomes True Lancer later on.