RWBY: Heroes United

Ben 10, wielder of the Ultimatrix, has gone on some crazy adventures including traveling to a parallel universe (Generator Rex). But this one has got to be his craziest one yet. Ben Tennyson has landed yet in another universe, the mysterious World of Remnant, a place that is inhabited by Humans, Faunus, and the Creatures of Grimm. Along the way he'll learn to work together with Team RWBY and JNPR, while saving Remnant from falling to darkness by the mysterious Salem with the help of his new team, Team 10 with his friends Rex Salazar from his previous adventure and Zak Saturday the Cryptid Hero. However, he would learn about his special Destiny that would tie his fate to the entire Multiverse while starting his own Family... A Big Family with a lot of girls... Along with their crazy and Wild adventures.
(MAJOR AU where Omniverse didn't happen and Julie Yamamoto is going to be sharing him with Yang and Harem.)
[ Ben Tennyson X Yang Xiao Long X Harem Girls OC Cryptids X Rosario + Vampire Girls except Yukari]
[ Rex Salazar X Ruby Rose ]
[ Zak Saturday X Blake Belladonna ]

Ben 10: Ultimate Alien, Secret Saturdays, and Generator Rex are owned by Man of Action, Jay Stephens, and Cartoon Network.

RWBY is owned by Rooster Teeth Productions, LLC. and Monty Oum (RIP)
Rosario + Vampire is owned by Akihisa Ikeda and Funimation Entertainment
BlazBlue, Persona, Under Night In-Birth, and Akatsuki En-Eins are owned by Arc Systems Work, Atlus, French Bread, and Subtle Style.

(Please note I will have the Cryptids from Secret Saturdays and Rosario + Vampire Yokais coexist in the SS/B10 world as Cryptids.)

(Reminder: I will NOT tolerate Flame Comments. I am trying real hard to not make this boring. The BlazBlue Cross Tag Battle Chapter with RWBY is Canon. And for Smash Bros. Ultimate, like Kirby, I have very good reasons that this will NOT be complicated. Thank You.)

P.S. The Ben being an Anodite, I've made it so for the Plot he would be involved with Zak's Past Life as Kur.