A few of these are for the main story and several are optional, but you can replay every dungeon to gather the people you've missed. The guardians do not count for this achievement. This will unlock in Chapter 09 after you rescue Sei if you have gotten them all by that point.
- Mantohihi - Chapter 00. Memento Needed: Banana Pendant. First person you rescue as part of the story. (Unmissable)
- Doran - Chapter 01. Memento Needed: Clay Goblet. Second person you rescue as part of the story. (Unmissable)
- Ramu - Chapter 02. Memento Needed: Four Leaf Clover. Third person you rescue as part of the story. (Unmissable)
- Cuk - Chapter 02. Memento Needed: Bugs. In the 3rd area of Ramu's dungeon right before the boss fight, in a secret area. There is an arrow made of tall grass pointing to this area. You will not be able to do the ritual until Chapter 03. (Missable)
- Jub - Chapter 03. Memento Needed: Cabbage & Banana. While using a blue gem to transport yourself to different islands, eventually you will open a 2 red gem door after a bubble puzzle. Go around the right side and follow the north path to get to another blue gem transporter. Ride it to the left to the next island with the red flower piece, but on your way back aim for the next gem station north of where you started. Jub's soul is on this island. You will not be able to do the ritual until Chapter 04. (Missable)
- Adun - Chapter 04. Memento Needed: Magnifying Glass. He is your main objective for Chapter 04.
- Pipit - Chapter 04. Memento Needed: None. In the second area of Adun's dungeon, after using the teleporter, you are in a large new area. Keep going left until you find the hololog of Pipit with his soul locked behind a red gem door. Get a 9 on the puzzle cube and hit the red gem. This is the first soul you are able to retrieve without having a memento first. You will not be able to do the ritual until Chapter 05.
- Aliwin - Chapter 05. Memento Needed: Crown. He is your main objective for Chapter 05.
- Turbo - Chapter 05. Memento Needed: None. This dog's soul is found in the second area of Aliwin's dungeon. In the section with the bubble puzzle to hit the red gems, there is a total of three red gems. The one on the ledge north of the bubble gem is the one that opens the door to Turbo's soul. You will not be able to do the ritual until Chapter 06.
- Ube - Chapter 07. Memento Needed: Security Badge. He is your main objective for Chapter 07.
- Sasa - Chapter 07. Memento Needed: None. Her soul can be found in Ube's Dungeon. In the second area, go right past the three red gem door, there is a bubble gem puzzle to open the one red gem door that contains her soul. You will not be able to do the ritual until Chapter 08.
- Pati - Chapter 08. Memento Needed: Locket.
*** Spoiler - click to reveal ***He is your main objective for Chapter 08. You might THINK it's Rasen, but no, Rasen is dead and instead it is your father you rescue.
- Sei - Chapter 08. Memento Needed: None. Can be found in Rasen's Dungeon. In the second big area of the dungeon go right at the fork and follow the path. Before the fight room, go right into the grass by what looks like a crashed spaceship. There is a secret passage further behind it. Sei's soul lies in that room. You will not be able to do the ritual until Chapter 09.