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