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