Here is the full list of all 12 My journey to your world achievements.
Clear Sairu's third star stage
Clear Lune's third star stage
Clear Raiko's third star stage
Clear Neruha's third star stage
Clear Raeve's third star stage
Clear Stizeha's third star stage
Unlock Sairu on your ship
Unlock Lune on your ship
Unlock Raiko on your ship
Unlock Neruha on your ship
Unlock Raeve on your ship
Unlock stizeha on your ship