Written in the Sky

A detective's daughter picks up an alien mating ring out of pure nosiness and ends up permanently bonded to the alien princess who came to retrieve it. That's the whole premise, and it's played straight rather than as a joke.

Azure's curiosity gets her into trouble the moment she follows a strange figure through the night and finds a box she has no business touching. The ring inside can't be removed, and neither can Sienna, the Martian emperor's daughter now fated to be her lover on Earth. What starts as a break-in gone wrong turns into two girls stuck figuring out an arranged, otherworldly relationship at school and at home.

There's nothing to steer here. It's a kinetic novel, so you read Azure and Sienna's story panel by panel with no branching choices to make, following the two of them from that first panicked night through the romance the ring forces on them. The pace stays on the smaller, quieter moments between the leads rather than escalating into anything sprawling.