Honkai Impact: Lord of Darkness

[Time travel + system + fan creation + invincibility + multiple female protagonists + a small amount of OOC + determined not to dismantle all male and female CPs, mainly Siegfried and Cecilia] A boy with the same name as Ryuga in "Kamen Rider Ryuki" came to the world of "Honkai Impact 3" by an outrageous opportunity, and transformed into DarkKiva to protect all the good things in the world, and eventually became a king. (Because I read a lot of books and found that there were too few about Kiva. Even if I found them, they were updated slowly or even stopped. So on a whim, I planned to write a Kamen Rider and Honkai fanfic based on Kiva. Since this is my first time writing a book, I don't know if I can stick to it. I hope everyone can support it. In addition to DarkKiva, the protagonist can also transform into Kamen Rider IXA and Kamen Rider Ryuga, but mainly as Dark. Mainly Kiva. Later, it may be increased depending on the situation, but the main thing is to obtain other knight abilities.