Here is the full list of all 30 Mystery Chronicle: One Way Heroics achievements.
Win 10 online matches in a row.
Battle in 10 online matches.
Clear a world on Very Hard.
Defeat Fallen Angel Alma on Normal or higher difficulty.
Clear a world on Hard.
Clear a world on Normal.
Complete a quest that unlocks a class.
Defeat 200 monsters on 1 adventure.
Defeat 100 monsters on 1 adventure.
Take 3 Allies with you on your adventure.
Clear any world other than the tutorial on Easy.
Win an online match.
Battle another hero in an online match for the first time.
Expand the castle.
Gain ability to customize the castle.
Acquire all trophies.
Defeat Zeukrees, the Giant of Light.
Defeat Pluton.
Reach the End of the East.
Reach the End of Dreams.
Reach the end of the world.
Recruit all residents.
Unlock all classes.
Clear on Normal or higher difficulty with all classes.
Open 50 treasure chests on 1 adventure.
Open 100 treasure chests on 1 adventure.
Expand Dream Vault to maximum size.
Defeat the Bug Emperor.
Obtain an extra medal.
Unlock all epilogues.