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