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
Get all stars from Draculea
Draculea's Secret
Meet Draculea
Get all stars from Kinutanuki
Kinutanuki's Secret
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
Get all stars from Ouni
Ouni's Secret
Meet Ouni
Ungaikyu's Secret
Get all stars from Ungaikyu
Meet Ungaikyu
Get all stars from Ichiko
Ichiko's Secret
Meet Ichiko
Get all stars from Kudagitsune
Kuda's Secret
Meet Kudagitsune
Get all stars from Atake
Atake's Secret
Meet Atakemaru
Open the friend book(please install free DLC)
Kane's Secret
Get all stars from Kane
Neko's Magic
Use a hint in game
Meet Kanedama
Get all stars from Neko
Neko's Secret
Meet Neko
The Story
Yokai's Encounter