Here is the full list of all 17 Ys I Chronicles+ achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Complete Ys I on Nightmare difficulty.
Master every achievement in Ys I.
Complete Ys I Time Attack.
Unlock all details for all non-boss bestiary entries.
Completely fill the character notebook.
Listen to Reah recite her poem.
Rescue Luta Gemma from monsters in the field.
Receive a free Talwar prior to entering the tower.
"Measure" Feena in the creepiest way possible.
"Measure" Feena.
Level-up Feena.
Confuse and astound the townsfolk.
Drive a hard bargain with Pim.
Receive a free Short Sword.
Complete Ys I on any difficulty.
Max out your money.
Make Dogi break through three different walls.