Based on the erotic doujin game by ShiBoo!.

Rin Himesato is a shy, plain, and ordinary girl who is bothered by the fact that her boobs are just a little bit bigger than others. On her way home one day, she is attacked by Hamelder, an evil organization that has infested the town. She is in a desperate situation! The one who rescued her was a friend of justice and a senior student at school, Sumire Hiyama, known as Frostia, a magical fighting princess. Rin learns of Frostia's true identity and can't help but worry about her as she fights. Frostia's predicament also ignites a flame of justice in Rin's heart! "I want to be a magic fighting princess......!" The story of a magical heroine of justice who fights against an evil organization begins! Roaring, Lilustear's Special Move!! Explosively erotic big breasts shake, plump thighs peek from the skirt. All the combatants who have ascended "twice" are in ecstasy!?

(Source: Getchu, translated)