Here is the full list of all 39 Swords Souls: Neverseen achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Complete endless stage 120
Complete endless stage 100
Complete endless stage 80
Complete endless stage 60
Beat the final boss using only beginner armor and weapons
Complete endless stage 40
Complete the museum to 100%
Get all Soul Master medals in all training areas
Become friends with all mercenaries
Complete endless stage 20
Get three Combo medals of rank Soul Master
Become friends with two mercenaries
Become friends with a mercenary
Find all lost children
Defeat chapter 6 boss
Catch 11 different types of fish
Catch 8 different types of fish
Tame all pets
Defeat chapter 5 boss
Tame 8 pets
Trigger the Oof ring once
Defeat chapter 4 boss
Become Soul Master in all training areas
Defeat the Legendary Hunters
Defeat chapter 3 boss
Get three Combo medals of rank Platinum
Defeat chapter 2 boss
Tame 3 pets
Catch 3 different types of fish
Get three Combo medals of rank Gold
Get three Combo medals of rank Silver
Get 3 perfect in a row while fishing
Defeat chapter 1 boss
Get three Combo medals of rank Bronze
Juggle with the same coin 30 times
Juggle with the same coin 20 times
Juggle with the same coin 10 times
Defeat the Mama Mole
Get three Combo medals of rank Wood