In 'touhou crossover fanfiction', adaptation is a big theme. The Touhou characters need to adapt to the new environments of the crossover universes. Whether it's a high - tech sci - fi world or a medieval fantasy land, they have to learn new skills or use their existing ones in different ways. Additionally, mystery is often present as the characters try to figure out the secrets of the new world they've entered.
Another theme is cultural exchange. The RWBY world has its own set of values, cultures, and technologies, and Touhou has its own very distinct world of youkai and magic. Fanfictions often show how the characters from each world learn about and adapt to the other's culture. For example, a RWBY character might be fascinated by the way magic is used in Touhou. It can be really interesting to see how they incorporate elements of each other's worlds into their own understanding. And this can also lead to some character growth as they expand their perspectives.
One common theme is the restoration of balance. If a great evil has been done in the Touhou world, a fairy might be reincarnated to set things right. Another theme is the search for lost love. A fairy could be reincarnated in the hope of reuniting with a beloved from a past life. Also, the theme of self - discovery through reincarnation is quite popular. The fairy discovers new aspects of herself or her powers in each new life.
One common theme is mystery. Yukari is a very mysterious character in Touhou, so in the fanfiction, the relationship with the reader often involves uncovering secrets. Another theme is adventure. Since Yukari can traverse different realms, the reader often goes on exciting adventures with her. And of course, there's the theme of the supernatural, as both Yukari and the world of Touhou are full of supernatural elements.
One common theme is discovery. The OC often discovers the strange and wonderful world of Touhou through their interaction with Yukari. Another theme is power dynamics. Since Yukari is a powerful character, how the OC relates to her in terms of power is often explored, whether it's the OC being in awe of her power or gradually growing to match it. Also, the theme of mystery is prevalent as Yukari herself is a very mysterious character, and the OC usually has to unravel some of that mystery.
Perhaps 'Touhou in the Underground: A Crossover Fanfic' would work well. It gives a sense of the Touhou characters being in the Undertale setting.
Well, in Touhou Project crossover fanfiction, a cool concept is the combination of Touhou with modern-day settings like a big city. Imagine Marisa Kirisame flying her broomstick over skyscrapers. Also, crossovers with other video game worlds are great. For instance, Touhou characters in the world of Super Mario, where they might have to deal with Mario - style obstacles. It's all about mixing the familiar Touhou elements with something new and unexpected.
The unique elements also include the mixing of the two different types of enemies. You have the grotesque and often very large enemies from Dark Souls like the demons and dragons, and then you have the more fantastical and sometimes cute enemies from Touhou. In the crossover fanfiction, seeing how the characters from each side deal with the other side's enemies is really engaging. For example, a Dark Souls knight trying to figure out how to fight a mischievous youkai from Touhou. And the way the stories play with the concepts of souls in Dark Souls and the spiritual energy in Touhou is also quite special.
A plot could be that some of the Touhou characters accidentally end up in the Undertale world. They then have to find a way back home while also getting involved in the conflicts between the monsters and humans in Undertale.
One popular 'touhou crossover fanfiction' is the one that crosses over with 'Pokemon'. It's really cool to see the characters from Touhou in the Pokemon world, with unique storylines like Reimu becoming a Pokemon trainer. Another great one is the crossover with 'Final Fantasy'. The magic systems of both get intertwined in interesting ways.
A common theme is the struggle for acceptance. The minotaur, being a different and often feared creature, usually has to fight to be accepted in the new world or by the new group of characters it crosses over with.