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