The pale orange ball glittered before his eyes, pulsing with energy from a magical unknown source. He gingerly picked it up and slowly examined it. Could this be the ultimate treasure I've spent my life searching for? He smiled enigmatically, his face impassive and gentle, yet his mounting excitement could not be hidden by the twinkle in his golden brown eyes. There were seven stars imprinted on the ball, glowing red before him. That means there must be six others, he mused, a crafty smirk crossing his smooth, beautiful face. Then I must have them all.

The nimble youko thief slipped the orange ball in a pack slung to his side, and with a stealthy flourish, he was gone.

A graceful warrior--fast, agile, and incredibly strong. Kaio-sama placed a finger on his forehead. It was time to contact Son Gokou.

"Nani?! Ano, Kaio-sama! Is something wrong?" Gokou's face held his usual cheery expression, and yet the tiniest of frowns marked the corners of his mouth. The summons must mean something dire.

"Someone has gone in search of the Dragon Balls! You must find him before he gets away!"

"The Dragon Balls? You mean we have to stop this person from summoning Shenlon?"

"It isn't that simple. This stranger is a demon, and he comes from a different dimension. A dimension portal opened up somewhere in the barren mountains to the west, and he must've stepped through. He seems to know the secret to summoning the Dragon Lord. But what his wish will be, I cannot begin to guess."

"We'll go after him then with Bulma's Dragon Radar. Dewa, sayonara!"

"Otou-san? That was Kaio-sama?" A boy dressed in blue slowly walked toward Gokou. Gokou smiled at his son. At twelve, the boy was already a strong and skilled fighter, far from the crybaby of his childhood days. He would prove to be a valuable ally in the oncoming battle with Cell and the androids. But for now, they had a mission to fulfill.

"So desu, Gohan. The Dragon Balls are being gathered by a demon, and we have to find him and stop him from calling Shenlon."

"A demon?! Honto ni?! May I come, Otou-san? I'd like to help search for him and help you fight."

"Come on," Gokou smiled at his son's courage and gently gripped his shoulder. "We have to call the others and begin the search for this thief."

He spread the seven glittering balls before him, awed at the way they sparkled in the night. They were pretty, certainly, yet he felt that there was a power hidden within that had to be summoned. How, I wonder. The balls continued their eerie glow, and Youko Kurama's brows knitted. Perhaps a pattern of some sort. I have to arrange them. But how? The allure of power beckoned to him. The thief from Makai smiled at the thought of this precious treasure that he had recently acquired.

Suddenly, he paused, and went still. There were beings coming toward him, and from what he could sense, they were very powerful. He debated with himself whether to stay or flee. Whatever this strange world he had woken up in, he hadn't encountered a fighter worthy of the name so far. A few puny ningen that he had put to sleep when they had interrupted in his search had been all. Yet he couldn't discount the possibility that there were powerful warriors in this world. Such a presumption would be dangerous on his part.

What would the thief do now? He smiled grimly to himself, aware that even his birth into a ningen body had not dulled his desire for the thrill of the chase, for the charm of danger. But he had survived for as long as he had on wit and cunning, and his senses were telling him to flee for now. Maybe I'll fight them another time. Youko Kurama placed the balls in his pack, then leapt into the portal he had spotted into the unknown beyond.

"Masaka!" Trunks stared at the suddenly blank Dragon Radar, where a few seconds ago, seven points of light had been indicated. "The signal vanished!"

"Fukano na," fumed Vegeta, who flew along silently beside his son. "Maybe that Dragon Radar of Bulma suddenly broke down or something. The Dragon Balls couldn't just vanish, and it appears that Shenlon hasn't been summoned, at least."

"No, I think the radar's okay," Trunks face was grim. "I think it indicates that the thief is no longer in chikyuu."

"Nani?! But where would he go?" Gohan exclaimed, puzzled and disappointed that their search had ended so quickly.

"Hn…Kaio-sama mentioned something about a dimension rift of something…" Gokou mused. "Maybe that has something to do with it."

"Feh, it could be some sort of trick to mislead us," Vegeta said, frowning yet introspective. "Or this thief could have gone back where he came from."

"It could be that, Otou-san," Trunks stated, still staring at the Dragon Radar. "Maybe we can find clues if we go to the site where the Dragon Balls were detected last."

The others nodded in agreement, and before long, they were descending to the site where the youko thief had been earlier. Trunks bent and examined the ground, and found faint round imprints. He also detected a ki signature that had departed not long before.

"He's obviously been here," Trunks remarked quietly, still bent on examining the ground. "He's left few traces though, and that shows that he is highly skilled, if anything."

"Skilled or not, he probably has the Dragon Balls with him." Vegeta stated flatly, ignoring the purple-haired youth beside him, instead intently studying the surroundings. His brow was wrinkled in concentration, and Trunks looked up to find his taciturn father silently brooding.

"Vegeta-san, what's--" Gohan began, but Vegeta waved him off with a curt gesture. Gohan followed the Saiyan Prince's gaze, which came to rest on a rock fissure located not too far away.

"There." Vegeta simply stated, and he walked briskly in the direction he had stated. The others followed, curious as well as exasperated over their companion's grudging silence.

When they neared the outcropping, they detected a small slice in the fissure. Gohan impulsively passed his hand over the hole, and was surprised when his hand was met with a small jolt of energy. He deftly pressed on, and his hand passed through into the black space.

"So ka," Trunks muttered, amazed. "It's a dimension portal. But a well-hidden one. This was where the thief must've passed through."

"Then let's go through and find the thief," Gokou said, his face grim and foreboding. "There's no telling how long before he summons the Dragon Lord."

"Hmph, you might be right for one, Kakarotto," Vegeta stated, his face lit with an ironic smile. "We must find this thief and get the Dragon Balls as soon as we can."

The four Z warriors stepped into the portal, into the unknown dangers and adventures that lay beyond.

There. The first part of the crossover. This is a non-yaoi story (at least so far) involving Kurama and the other rei kai tantei. This also involves the Saiyan warriors from Dragon Ball Z. All of ningenkai and makai is about to break loose when these characters meet. ;)

The setting of this story is about at the time before Cell arrives in Dragon Ball Z, and a little after the Ankoku Bujutsukai in Yu Yu Hakusho. So how does Kurama get switched into his youko form at the time he arrives at chikyuu? I have no idea. ;) This story is speculation on my part. It's a "what-if" take on what will happen when two worlds collide and incredibly powerful warriors meet. How this develops from here, I'm still working out at the moment.

Dragon Ball Z is a copyright of Akira Toriyama, and Yu Yu Hakusho was created by Yoshihiro Togashi. This fanfic is for entertainment purposes only.