Here is the full list of all 49 Yokai's Secret achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Yokai's Secret
Get all colors back
Draculea's Secret
Get all stars from Draculea
Meet Draculea
Kinutanuki's Secret
Get all stars from Kinutanuki
Meet Kinutanuki
Amanozako's Secret
Get all stars from Amanozako
Meet Amanozako
Kawauso's Secret
Get all stars from Kawauso
Meet Kawauso
Akakami's Secret
Get all stars from Akakami
Meet Akakami
Kurage's Secret
Get all stars from Kurage
Meet Kuragenohinotama
Kinoko's Secret
Get all stars from Kinoko
Meet Kinoko
Ouni's Secret
Get all stars from Ouni
Meet Ouni
Ungaikyu's Secret
Get all stars from Ungaikyu
Meet Ungaikyu
Ichiko's Secret
Get all stars from Ichiko
Meet Ichiko
Use a hint in game
Get all stars from Kudagitsune
Kuda's Secret
Neko's Magic
Meet Kudagitsune
Get all stars from Atake
Atake's Secret
Meet Atakemaru
Open the friend book(please install free DLC)
Get all stars from Kane
Kane's Secret
Meet Kanedama
Get all stars from Neko
Neko's Secret
Meet Neko
The Story
Yokai's Encounter