Miraculous Ladybug: Spots and Cat Kisses

[Ladybug and Cat Noir stay together + realistic tone + sci-fi + a little angst + happy ending]

The story begins after the love quadrangle involving Marinette and Adrien has developed, during the period when the black cat Noir and Marinette begin falling for each other.

A rift in space and time appears unexpectedly one night in Paris, making them both realize that the person they've been searching for all along is each other. They confess their feelings, but an unexpected turn of events sweeps them into a fictional illusion. They come to understand love for all humanity while also finding true love. In the end, they join hands to protect the parallel worlds.