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