Kamen Rider: Beginning as the Female White Mage

[Kamen Rider + gender transformation + gender-bending romance + dual protagonists, one-on-one + no System + not overpowered + original setting]

(Mostly from the heroine's perspective, with both action and everyday life. Please go easy on the blurb.)

(The main setting takes center stage, though the characters will travel through various Kamen Rider worlds in the early and middle arcs.)

The sharp-tongued amnesiac An Lan settles in with the Kitano family, searching for her lost past with the help of a White Wizard belt. She never expected the boy she looked down on, her housemate, to become a completely different person overnight, muttering strange things like “transmigrate” and “Where's my System?” His luck even skyrockets, and he becomes Kamen Rider Kuuga!

Meanwhile, the world begins to undergo drastic changes. Nothing is the same anymore.