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