Disclaimer: I do not own Dragon Ball, or any of its associated characters and lore. That right belongs to Akira Toriyama.
The New Demon King from Planet Vegeta
King Castle, Central City, Earth, Age 753, May 9
Upon crash-landing on Earth as a newborn Saiyan scientifically enhanced into a preteen in appearance and mental faculties, Kakarot was soon found by a surviving son of the onetime Demon King Piccolo, the pterodactyl-like Ukulele. Having survived in hiding for over two centuries, Ukulele, who was identified by Kakarot's Scouter as a Mutated Namekian, found a potential asset in the Saiyan child tasked with Earth's conquest as much as Kakarot saw in Ukulele a chance to grow stronger to ensure the planet was properly acquired by the Frieza Force.
Although Kakarot was unable to make contact with his superiors in the sixteen following years, he and Ukulele nonetheless trained hard, made observations of how global society was developing, and gathered allies to aid them into finding the electric rice cooker Piccolo was sealed in. Convincing said allies to assist them took effort, but working side by side, they were at last able to free Piccolo, who had recently overthrown King Furry and in respect to Ukulele's bargaining, had decided to honor his promises to the Pilaf Gang as well as the other Demon Clans led by the Vampiric Count Lucifer and the minor Demon Realm King Shula.
"You seem pretty eager of things to come, Kakarot." Ukulele was telling his young comrade as they looked over Central City from King Castle's balcony.
Kakarot smirked. "How can I not be? The Earth is ours and King Piccolo said that I can run my own Demon Clan soon enough."
"Your own Demon Clan?" Ukulele said in surprise with a prideful smile. "Not bad. You've come a long way from when I first got you out of that spaceship."
Kakarot scoffed good naturedly. "Don't flatter yourself, you old dinosaur-shaped Namekian."
Sharing a quick laugh, Kakarot then parted ways with Ukulele to venture further into the castle where he came across the finely dressed Lucifer.
"Greetings, Kakarot." Lucifer politely said to the half-amused Saiyan before he then added. "I trust that an Earth shared by five rulers will be a satisfactory balance for all parties involved?"
Kakarot grunted, but nodded in understanding. "No need to worry, Count. So long as nobody rocks the boat, it should be easy enough to manage. Now, if you'll excuse me, I'd like to see something else at moment. No offense intended."
Lucifer bowed his head and allowed Kakarot to take his leave. Walking along, he soon met with the Human-like Demoness he wanted to see. Shula's then subordinate, Melee.
"I trust it's going well, Kakarot?" Melee asked him with a smile when they came face to face.
Kakarot grinned. "Definitely, Melee. Getting ready to work for me soon?"
"Of course, my King." Melee replied with a kiss on the Saiyan's right cheek.
Thought of a Demon Clan Goku/Kakarot idea a while back from speculating on SpaceBattles and reading a similar prompt on DeviantArt by JokuSSJ, even if it's under Red Ribbon Kakarot or something on that last one. Speaking of ideas, I've recently been rethinking my approach to writing longer Dragon Ball stories like Kakarot Brief. As much as I want to depict Goku/Kakarot being brought up by other people than Grandpa Gohan such as the Brief family, Pilaf Gang, Red Ribbon Army, and Kami as well as aged up so that he could become better romantically involved with female characters other than Chi-Chi, I rethought back about how being Goku was a big part of his character, and I don't really want Kakarot Brief to be the Shonen version of The Testament of Sister New Devil, especially since I can always give Goku/Kakarot the same enhanced growth as I have done in this one-shot and several others. However, I'll still continue Kakarot Brief as a short story if nothing else like I did with The Supreme Being Duo and how I intend to do with some Fairy Tail Different Guild Natsu AUs.