Yagi Jubei is the main antagonist in Ganbare Goemon: Sarawareta Ebisumaru! He kidnaps Ebisumaru and sends a letter to Goemon where he asks him to go to a town called Hizen if he ever wants to see him alive again, thus setting the events of the game to unfold.
It's another beautiful morning in Hagure, a small town at the outskirts of Edo, when a messenger suddenly interrupts into Goemon's house and gives him a letter. The still sleepy Goemon wakes up and starts to read:
"My name is Yagi Jubei.
Sir, we are holding your friend Ebisumaru.
If you want him returned in good health, your presence is requested in Hizen.
If you do not come, you can assume Ebisumaru is no longer among the living!".
So, with these threatening words, Goemon sets on his way to rescue his good ninja friend, Ebisumaru.