Disclaimer: I do not own Edens Zero, or any of its associated characters and lore. That right belongs to Hiro Mashima.
A Roguish Outlaw
Rogue Out Headquarters, Planet Guilst, Sakura Cosmos, X492
In the time he had been made a mercenary of the Rogue Out squad in service to the pretender who styled herself as "Sister" of the Four Shining Stars, Mosco had been secretly fighting against his own reprogramming which prompted him to seek out his retired superior, the Demon King Ziggy, for help. Upon his secret arrival to the abandoned amusement park on Planet Granbell, however, Mosco learned to his disappointment and sadness that Ziggy had shut down years before. Nonetheless, he was able to find Ziggy's successor, a young Human named Shiki, and after some convincing, he was persuaded to come with Mosco to Guilst to reawaken the real Sister Ivry and complete their original mission on the planet.
"And then we'll head back to fix my friends at home, right?" Shiki asked for confirmation as they snuck through the abandoned church that served as Rogue Out's headquarters.
"Right, Moscoy, now hush-hush." Mosco replied as quickly and silently as he could. While it looked like no other Rogue Out members were around at the moment, it was better to be safe than sorry.
Using the hidden elevator to get to the basement, they soon found the machine that had been transferring Ivry's powers to her imposter while she herself was suspended in its grasp. With Mosco's reprogramming preventing him from releasing Ivry himself, he left it to Shiki to do the deed. Upon untangling Ivry from the machine, she soon woke up weary, but no worse for wear.
"Mosco?" Ivry said first upon standing on her own feet. "What happened?
"No time to explain now, Moscoy. We have to leave right away."
With Mosco leading the way, both Shiki and Sister Ivry took turns introducing each other as quick as they were able to, given the circumstances.
I know I didn't really depict the other members of Rogue Out, or even make a Shiki/Ivry/Sister Impersonator lemon like I wanted to, but I did what I could. Still wish the founder of Rogue Out was properly identified, but here's hoping some information like that will come along in time. I can actually imagine a true story that has Rogue Out recruit Shiki from Granbell and with the False Sister alongside him, they would've gotten to work building quite the power base similar to whatever Ziggy had, but remade in Shiki's image. However, just as Lucy Heartfilia from Fairy Tail wouldn't have gotten in any adventures without meeting Natsu Dragneel, I don't think Shiki would have the same voyages if he hadn't been picked up by Rebecca.