The threshold for entering Ryuchi Cave and signing a contract isn't so low that just any common ninja can do it, nor is it so high that one must be an exceptionally powerful expert. One only needs the basic inner qualities of a strong person, or to already possess some of their potential, to have a good chance of passing the trials.
In the original timeline, during the Shippuden era alone, there were four who officially became contractors of Ryuchi Cave: Orochimaru, Yakushi Kabuto, and Uchiha Sasuke were all exceptionally powerful shinobi. Even the weakest, Anko Mitarashi, was at least a Tokubetsu Jonin, though she encountered Orochimaru's defection during her most critical stage of growth.
Unwilling to follow Orochimaru and politically suppressed by the Konoha higher-ups due to her status as his disciple, she was unable to receive proper training. Ultimately, her talent was wasted, and she became an ordinary ninja—stronger than those below her, but lacking compared to the elite.
The Three Great Sage Regions are actually all similar in this regard; it's just that Ryuchi Cave's methods are much more brutal and direct.
Ten seconds later, Uzuki Ruri opened her eyes, her gaze appearing dazed for a moment.
"Gen? Was that really a Genjutsu just now?"
"Yeah, now we're just waiting for Enjun."
Just as he finished speaking, Sarutobi Enjun opened his eyes, just a few seconds after Uzuki Ruri. His resistance to Genjutsu was slightly worse than Ruri's, but overall, he was still qualified; at least he could withstand this trial.
"So now, this should be the final trial, right?"
Uchiha Gen looked up at Tagitsuhime.
"Tsk, boring. Your trial is probably useless too. You'd be better off playing with your jigsaw puzzle," the latter said, looking into the mist and shouting.
"Oh, you'll know once they try it."
A Snake Princess in the form of a young girl floated out of the mist. She was the last of the Three Great Snake Princesses of Ryuchi Cave, Ichikishimahime. The loli Snake Princess held her head with both hands, floating in the air as if swimming on her back while pointing into the fog.
"There's a maze in there that I painstakingly designed. As long as you can walk out, you'll be able to see the White Snake Sage and complete the final trial!"
"A maze? Isn't that simple? I remember a trick: as long as you keep turning right, you can get out of any maze!" Sarutobi Enjun said excitedly.
"Hehe, I've heard of that too. You're more than welcome to try!" The loli Snake Princess giggled.
Gen pulled a compass from his ninja tool pouch and found that the magnetic field here was chaotic, with the needle spinning incessantly. He looked up, trying his best to confirm the direction, and then spoke.
"Let's go in. Follow my lead."
The group walked quickly into the maze and reached the exit in less than two minutes.
"See, I told you it was useless. Using your jigsaw puzzle game might have actually tricked them; at least it's worked before," Tagitsuhime said, spreading her hands.
"How can this be!" Ichikishimahime was dejected.
Although she could freely manipulate inorganic matter while using Ryuchi Cave Sage Art to easily create a maze, having it solved so quickly made her quite frustrated.
"Gen, how did you do it? You actually got out so fast!" Sarutobi Enjun marveled at his companion.
"It's simple. It's actually an upgraded version of your right-hand rule. After choosing a direction, go that way as much as possible. When you hit a dead end, use the Pledge Algorithm: turn right and follow the wall on your left until your orientation matches the original direction you chose, then continue as before."
"This method might not solve every maze, but it's definitely enough to handle the vast majority of similar situations."
Gen closed the map he had just hand-drawn, looked at the pavilion appearing in the distance, and spoke to Sarutobi Enjun. He had happened to see this maze algorithm in his previous life, which could be used to solve most mazes, provided the user had strong spatial memory and directional judgment.
The former could be compensated for by hand-drawing a map, and the latter happened to be covered by his sensory abilities.
At that moment, all Three Great Snake Princesses gathered in front of the pavilion. This was the core inner sanctum of Ryuchi Cave. Although it wasn't as magnificent as the palace Tagorihime had created with Genjutsu, it was quite elegant.
"Creak..."
The pavilion's doors were slowly pushed open. The Three Great Snake Princesses lined up and invited the trio inside, leading them to the second floor. In the center, a thick white snake was curled up, resting on a stone bed and lazily flicking its tongue.
Seeing the visitors, it slowly sat up, its upper body transforming into an old woman who looked advanced in years.
"So you three are Orochimaru's students. Come closer and let this old lady have a look."
Gen and the others glanced at each other and stepped forward slowly.
"Greetings, White Snake Sage."
"Hmm... this girl's skin is fair and tender; she should taste quite good. This little monkey is a bit lacking, but he'll definitely be chewy. And you... tsk, this generation's Indra... hmm? No, it seems this old lady misjudged."
The White Snake Sage slithered down from the stone bed, flicking her tongue as she circled Gen again and again, muttering something under her breath. Gen tried his best to listen, but he couldn't understand.
"Forget it, I can't be bothered with you. Do whatever you like. If you're not afraid of death, you can come to me one day to learn Sage Art. Now, get out."
The White Snake Sage grumbled as she walked back to the bed, waving them away irritably. The three felt a powerful gust of wind hit them; it didn't harm their bodies but instead pushed them out of Ryuchi Cave.
"Bang!"
The door slammed shut.
"White Snake Sage, this..." Tagorihime asked hesitantly.
"I understand that family's affairs less and less, and I don't want to get as involved as that toad. Just treat them as summoning contractors like Orochimaru. Be careful not to kill that Indra descendant."
The Three Great Snake Princesses looked at each other, speechless for a moment.
Outside the pavilion, Gen felt like he was about to land on his back, so he performed a nimble mid-air flip and landed steadily in a half-crouch.
"Gen, why did the White Snake Sage's attitude suddenly change? And who is Indra?" Uzuki Ruri asked curiously.
"Maybe it's because I'm from the Uchiha Clan. Orochimaru-sensei said the White Snake Sage has lived for over a thousand years, and Lord Indra is an ancestor recorded in our clan who was active a millennium ago. Perhaps this Sage has some lingering grievances with the legendary Indra."
Gen casually came up with a plausible-sounding explanation.