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