Anime Crossover: I'm Just a Passing Traveler

One day in the future, the history of the knights is scattered by someone with ulterior motives. To destroy the knights' existence, they disperse the watch face representing that history across various worlds. With each watch activated, that piece of knightly history begins to erode that world, ultimately erasing it at the cost of an entire world. Meanwhile, a mysterious young man named Kadoya arrives in Shuchiin. What is his true identity? His mission to collect knightly history across 38 worlds is nearing completion, and he will soon find the meaning of his journey.

Currently in the world: Fate (Rider Rush+). When the Holy Grail War in Fuyuki City unexpectedly intertwines with the Knight War in the Mirror World, an unusual Holy Grail War of fourteen knights in a chaotic battle quietly begins. Magicians and Kamen Riders, Contract Beasts and Servants, the Mirror World and the real world—the originally parallel laws collide here, bringing chaos and miracles.

Kamen Rider + Fate + Oregairu + Date A Live + Kaguya-sama: Love Is War + My Favorite + Ellie-chan... and so on and so forth.