Joker is the main villain from Emelia's storyline in SaGa Frontier. Joker is a strange masked individual, whom Emelia witnessed murdering her boyfriend Ren. Emelia, however, ended framed for the crime and imprisoned. After escaping, she joins Gradius, a secret police force made by ex-criminals, and chases Joker to learn his motives. She learns Joker was working with Trinity, as they were searching for Cube, a mysterious power source.
When the current leader of Trinity is overthrown by Mondo, he sends Joker to Yorkland, telling him Cube was located there. Mondo lets Emelia infiltrate his base, and tells her he made a set-up for Joker, as he needed Gradius to get rid of him, as he was becoming a nuisance for Trinity. Emelia finally confronts Joker in Yorkland's church, where she points her gun to him, while he threatens her to give Cube to him.
Just then Emelia hears her boyfriend Ren's voice, telling her to shoot the mask. As it turned out, Joker was actually Ren, who got possessed by a mask while investigating Cube. Emelia hesitates, but as Joker gets near she shoots him, taking off the mask and destroying it, thus freeing Ren from the possession.