Yuka Terasaki

Yuka Terasaki is the Master of the Assassin Class Servant during the First Holy Grail War of Fate/Eternity. He's the youngest master that ever took part in the wars, only 13 years old, and is also cowardly and terrified of direct confrontations; because of this, he was raised as an assassin his entire life, which is why he aimed to summon Assassin during the war.