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.
Neko's Magic
Yokai's Secret
Get all colors back
Draculea's Secret
Get all stars from Draculea
Meet Draculea
Get all stars from Kinutanuki
Kinutanuki's Secret
Meet Kinutanuki
Get all stars from Amanozako
Amanozako's Secret
Meet Amanozako
Kawauso's Secret
Get all stars from Kawauso
Meet Kawauso
Get all stars from Akakami
Akakami's Secret
Meet Akakami
Get all stars from Kurage
Meet Kinoko
Kinoko's Secret
Get all stars from Kinoko
Meet Kuragenohinotama
Kurage's Secret
Ouni's Secret
Get all stars from Ouni
Meet Ouni
Get all stars from Ungaikyu
Ungaikyu's Secret
Open the friend book(please install free DLC)
Meet Ungaikyu
Get all stars from Ichiko
Ichiko's Secret
Use a hint in game
Meet Ichiko
Kuda's Secret
Get all stars from Kudagitsune
Meet Kudagitsune
Atake's Secret
Get all stars from Atake
Meet Atakemaru
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