Here is the full list of all 50 I am Setsuna achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Obtained all achievements.
Fluxation occurred 200 times.
Defeated the Dark Samsara's final form.
Fluxation occurred ten times in Support Spritnite.
Defeated the Ruler of Time.
Obtained the Genesis spritnite.
Added maximum Fluxes to a spritnite stone.
Defeated all the Spritnite-Eaten Monsters.
Defeated all members of the Hoot-Hoot species.
Obtained the Dragnarok spritnite.
Obtained the Doom spritnite.
Obtained the Eclipse spritnite.
Obtained the Rebellion spritnite.
Obtained the Gearadia spritnite.
Obtained the Holy Light spritnite.
Defeated all members of the Pengy species.
Sailed on the exploratory ship.
Saw the Laniff Ruins.
Saw the Moolbeld Ruins.
Ate Gatherington Fries.
Ate Starberry Cake.
Ate Nive Vegetable Stew.
Ate Gaia's Blessings Stew.
Ate Horse Oak Casserole.
Listened to all the youth's lines and defeated him.
Met the youth.
Used one megalixir.
Met Eutess.
Saw ???.
Met Rhydderch.
Fluxation occurred four times in a single battle.
Inflicted 500 damage in a single hit.
Inflicted 1000 damage in a single hit.
Used combos in Momentum mode 30 times.
Met Sayagi.
Fluxation occurred ten times in Command Spritnite.
Used Momentum mode 100 times.
Made one monster drop eight materials at once.
Met Cornelius.
Saw the Apparth Ruins.
Defeated enemies with all Kill types.
Used Momentum mode ten times in a single battle.
Met Hydor.
Met Akash.
Defeated ten enemies with Over Kill.
Made one monster drop four materials at once.
Met Freyja.
Defeated ten enemies with Exact Kill.
Met Raishin.
Met Hapsper.