Here is the full list of all 20 Kaiju Princess achievements.
Obtain Popsicle Kaiju Doll
First Quota Reached
Reach Orgasm x2
Obtain the Witch Outfit
Cum with Me
First Time
Obtain the Maid Outfit
Obtain the Magical Teen Outfit
Obtain the Competition Swimsuit
Obtain the Bikini
Reach Mouth Accomplishment Lv.3
Reach Breast Accomplishment Lv.3
Reach Clit Accomplishment Lv.3
Reach Vagina Accomplishment Lv.3
Reach Orgasm x4
Reach Orgasm x8
Kisses x1000
Obtain Festival Fan Doll
Obtain Tilapia Doll
Obtain Black Cat Cape Doll