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