Here is the full list of all 43 The Spectral Web: Hitodama achievements.
Defeat Jack
Defeat Will.
Defeat Seine.
Defeat Loire.
Clear a Wisp double battle.
Clear the Riviere double battle.
Complete Hito's story.
Attain 100% completion of the main Labyrinth.
Complete a run with six or fewer life orbs, starting MP, and less than 10 coins.
Complete a run in under one hour.
Defeat Jack on Normal or higher without taking damage.
Defeat Will on Normal or higher without taking damage.
Defeat Seine on Normal or higher without taking damage.
Defeat Loire on Normal or higher without taking damage.
Clear a Wisp double battle on Normal or higher without taking damage.
Clear the Riviere double battle on Normal or higher without taking damage.
Clear a Wisp double battle without using water or darkness.
Fill the Bestiary with at least one of every category of monster.
Fully complete the Bestiary.
Clear a Wisp double battle on Sadistic.
Clear the Riviere double battle on Sadistic.