Kourin Tenshi En Ciel Rena by Triangle - Adult Sex Game

Rina Kanoe is a diligent girl student who lives alone at the Zero Police artificial city controlled by the largest international corporation.
However, there have been a lot of demon appearance incidents lately. One night she witnesses a girl fighting a monster and getting defeated.
Rina picks up a card that fighter girl drops and transforms into a pretty warrior girl.
Rina manages to beat the monster by following the defeated girl instructions.
The girl turns out to be a runaway from another world. No one else is able to use these magic cards, so Rina agrees to stand up and protect justice in the city.