A/N: just know I'm basing this off of zi-o vs decade so...yeah let's get on with this.

ace p.o.v:

ace: so this is union huh?

(union high looks like U.A from bnha)

time skip----------------

ozpin: so you want to join union am i correct?

Ace: yes sir you are.

ozpin: i sense great energy from you, do you mind demonstrating.

ace: later

time skip to training------------------

all might: hello students today we have a new student, now if you like to introduce yourself

ace: hello everyone my name is ace rose, ruby and yang's brother and can i challenge my sis

all might: if it's okay with miss rose

ruby: yeah it is

glenda: all right it's ruby rose vs Ace rose

saber: i wonder who will win

Y/n: it would be ruby i mean she is a kamen rider now.

sclash driver: rose jelly

ruby: henshin

driver: blooming rose in ruby

(same form)

ruby: like my new power bro

ace: yeah but you will be surprised by this

----ZI-O-------

everyone( except the cast of rwby): huh!?!?

ace: henshin

Driver: Kamen rider~~ zi-o

he turns into = Kamen rider dark zi-o

ace: it's show time!!!!

(ignore geiz, it's the ryuga armor instead of ryuki survive)

ace: lets end this

Zikan Girade(ken): Knight survive time break

Y/n: how!!!!!

chara19x: this is going to be a 3 part series so the final part will be longer and sorry i haven't been updating the story is just i have been busy with high school i hope you enjoy this chapter>