This takes place after they defeated Sensui but Yusuke never turned into a demon. He's still a human in this version.
Botan flew over Tokyo, looking for Yusuke since Koenma told her to keep an eye on him and any suspicious behavior. She flew to Yusuke's school as fast as she could. "Yusuke!" she shouted.
She flew over and saw he was fast asleep on the roof of his school. "What Botan, I'm in a bad mood," he replied coldly.
"Kurama's was kidnapped by demons!" she shouted at him as she landed on her ore, "Listen to me!"
"Nice try, Botan," Yusuke said, "I'm not moving from this spot. Kurama's way too smart to get kidnapped."
Botan said, "Koenma got a message from the Okaharu group with a picture of Kurama in chains and bleeding. He needs your help!"
He sat up and asked, "Are you serious?"
"Hey!" Kuwabara shouted from the lower part of the roof, "What are you guys planning up there? I thought we were a team now ever since we defeated Sensui." He walked over to the ladder and started climbing up to greet them.
Botan said, "Kuwabara, Kurama's been kidnapped!"
"What?" he asked, "Is this crazy-day or something, how would he get kidnapped?"
"We're not sure how this happened," she explained, "but this group of demons isn't going to stop there. They're rounding up as many demons in human world as they can which means-"
"Hiei is going to be their next target," Yusuke finished, "they might even try going after Yukina."
Botan asked, "Now you're going to take me seriously? We have to find Hiei."
Kuwabara said, "The only one who actually spends time with him is Kurama. He'd be the one to know where he is. Maybe we should try that whistle thing again."
"The what?" Yusuke asked.
"Don't you remember anything?" Botan shouted, "It's the mystic whistle he's talking about!" She glared at him.
"Okay, calm the hell down," he said.
Kuwabara said, "Didn't you say you never told Urameshi about that one because you never needed to?" He narrowed his eyes at her.
"Uh," she said nervously, "well, maybe. Anyway, the mystic whistle makes a sound only demons can hear. I'll have to go back to spirit world in order to fetch it."
"No need," Hiei's voice came from behind Yusuke on the roof.
Kuwabara and Botan nearly fell over from the shock. "Hey, Hiei," Yusuke replied as he turned around, "Heard us talking about you?"
"What the heck shorty!" Kuwabara shouted, "Where did you just come from?"
"Seriously, Hiei," Botan said, "you scared us half to death!"
"Kurama's been kidnapped by thugs," he said, "and it looks like whoever did it is targeting demons. I just had to kill one that was tracking me before I came here. I figured since you're a spirit world lacky you'd know what was going on."
Yusuke said, "That's all we know."
Botan said, "It's the Okaharu gang! Haven't you been paying attention to me at all? And since they're targeting demons they might go after Yukina too."
"I won't let that happen," Hiei said.
Kuwabara asked, "So where's Kurama now? Does anyone know?" They all looked at Botan.
"Well," she said, "Koenma's the one with all of the information, I was just supposed to bring you guys together and since you're all here now." She brought out her ore. "Come on, what are we waiting for?"
Koenma explained from his desk in spirit world to the four of them, "Kurama was kidnapped by the Okaharu group, a group of demons that has been trying to take over living world for quite some time."
Yusuke asked, "Then why didn't you say anything before?"
"To be honest," he replied, "it started happening at the time you got hit by a car Yusuke. It's what made me decide I need a spirit detective again."
"What?" he asked.
Kuwabara asked, "All the way back then, these jokers have been causing trouble? Why is it only an issue now?"
Koenma explained, "They moved so slowly, and right after Yusuke became a detective Hiei and Kurama stole the artifacts of darkness, then after that a demon wanted to take over Genkai's technique and I think all of you know the rest, maze castle, rescuing Yukina, and so on. So much has been happening that I haven't been able to keep an eye on them and because of that they managed to kidnap Kurama. Take a look." He made an image appear on the screen behind them.
They turned around and saw Kurama's wrists shackled over his head, he was hanging in front of a large pole and was covered in wounds that were bleeding. "Kurama," Yusuke whispered.
"What are they going to do to him?" Hiei asked as he turned away.
"We can't tell from here," Koenma replied, "that's where all of you come in."
Yusuke demanded, "Where are they?"