This is a novel with way too many elements.
According to the voice recorder: Beep.
In a parallel world of Date A Live, there are five Spirits who call themselves the Messengers of Hell (five chuunibyou). They represent silver and black, black and gold, multicolored, gray and green, and colorless. Our protagonist, Liang Ji, a genius who can transform into Kamen Rider Decade, transmigrates to the world of Date A Live to cause trouble.
Calling yourself a genius? Have you no shame?
Quit your nagging. He's my little brother, the one who can transform into Kamen Rider Zi-O. He cried and begged me not to leave him, so, being the kindhearted person I am, I took him traveling with me.
I did no such thing!
Anyway, this is the story of how we're not only Kamen Riders, but Spirits too.