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Jack is first seen guarding the entrance to the village cemetery, saying that its too full of monsters for people to visit. When Quote informs him that Toroko has been kidnapped by Misery, he leaves his post to meet with King in the Assembly Hall to discuss what to do. Both agree to trade Sue for Toroko, since they view her as an outsider and the reason the Doctor is taking Mimiga from the village. After Quote finds the second key to Arthur's house and leaves the door unlocked, King and Jack wait for Sue to teleport back from the Egg Corridor to capture her and lock her in the village cage, waiting for the Doctor's minions to return to make the trade.
As Quote goes to Bushlands to rescue Sue's brother Kazuma in her place, Sue tells King and Jack the Doctor's plan to turn all the Mimiga into his personal army using Red Flowers. The two of them let Sue free, and Jack returns to the Assembly Hall, where he will talk about how Arthur managed to repel a Mimiga-eating Red Ogre from the village before he died.
After the Doctor obtains the red flowers and Quote is sent to the Labyrinth by Misery, Jack and all the other Mimiga are taken to the Plantation to start cultivating the plant. However, Jack defies her and Balrog, so he is put in prison, along with Sue and Mahin. After Quote is knocked out and imprisoned in the same cell, he will wake up to find that he and Mahin are the only ones left in the jail. Jack is not seen for the rest of the game.
|General||Mimiga Village • Mimiga • Balrog • Bubbline • Cemetery • Ma Pignon|
|Characters||King • Toroko • Mahin • Jack • Kanpachi • Sandaime • Misery • Little Man|
|Enemies||Egg Fish • Pignon • Gravekeeper|
|Items||Map System • Silver Locket • Arthur's Key • Beast Fang • Mushroom Badge • Booster v2.0|
|Interactive objects||Teleporter • Fireplace|
|Cave Story Characters|
|Protagonists||Quote • Curly Brace • Sue Sakamoto • King • Toroko • Kazuma Sakamoto • Professor Booster • Itoh • Momorin Sakamoto|
|Antagonists||Doctor • Misery • Balrog • Ballos|
|Others||Tetsuzou Kamadani • Jack • Mahin • Kanpachi • Sandaime • Arthur • Cthulhu • Santa • Chako • Malco • Colons • Jenka • Puppies • Chaba • Dr. Gero • Nurse Hasumi • Littles • Chie • Zett • Megane • Shovel Brigade • Numahachi • Ballos|
|Races||Robots • Mimiga • Humans • Cthulhu • Witches • Gaudi • Droll|