[Crossover] I Became a Sword Spirit and Joined the Demon Slayer Corps

Tian Shengmu Mei was a young lady from a □□ family. She had only planned to become an ordinary □□ big shot, but the moment she opened her eyes, she had transmigrated, and even changed species. She had become a sword spirit, and a level 1 one at that. Worst of all, a demon was chasing her down.

The sword spirit setting: She only gets injured when her true body is hurt, but she can only level up by fighting with her true body. Once she reaches the maximum level later on, she can switch to a Nichirin Blade to fight demons without getting hurt. Since her soul is human, she isn't so proud that she insists on fighting with her true body.

My personal headcanon is that this sword spirit can kill demons. Her power is connected to the sun, and her fighting ability is much greater than that of a Nichirin Blade. So even at level 1, killing ordinary demons without Blood Demon Arts is easy. If she gets hurt, it triggers True Sword's Critical Strike, multiplying her fighting ability by ten. But against an opponent who's too strong, she's still done for.

Since she isn't human, she heals through spiritual power. That's one of the main reasons she becomes a member of the Demon Slayer Corps: the head of the family and his wife both have spiritual power, and she is the only one who can heal her quickly. The treatment is similar to maintaining a sword, though ordinary bandaging works too, just more slowly. She still heals much faster than humans, and as long as her blade isn't broken, she can't die.

The □□ young lady setting: She's very skilled at kendo, but definitely not as good as Breathing Styles. She'll meet a trainer and learn a Breathing Style. For now, I've set it as Water Breathing. She kills demons to level up and return home. There is a quest System, but it's the kind that only reminds her of quest progress, like a robot, with no interaction.

The sword spirit setting comes from Touken Ranbu. This is an original sword [because who knows if Touken Ranbu will introduce a new sword later and prove me wrong]. Its type is an odachi, and its whole body is larger than the female lead's. She's 1.6 meters tall, so just use Hotarumaru as a reference.

Theme: I've gotten a tiny bit interested in writing Demon Slayer again