"You must be Sakura," said the minuscule carriage-sized slug, as Sakura slid down the trunk of the tree she'd just climbed. "Lady Tsunade sent word of you arrival, so I came to greet you."
Still in a state of shock after having seen the slug's true body, Sakura threw herself to the ground with a running start to perform the highest display of respect she could possibly demonstrate: a sliding dogeza.
"P-Pleased to meet you, L-Lady K-K-Katsuyu!" shouted Sakura, sliding a good five metres before grinding to a halt in front of the slug, her wide forehead grinding painfully against the ground. "Words cannot express how sorry I am for treating you with such disrespect earlier, and I hope I didn't keep you waiting!"
No wonder the original Sakura and Shizune treated Lady Katsuyu with such respect! Lady Katsuyu was bigger than anything they had ever seen in their lives!
"There's no need to apologise," said Mini-Katsuyu, cocking her head to the side cutely. "You just took me a bit by surprise when you grabbed my tail, that's all."
Sakura breathed a sigh of relief.
"You should probably get going, you have a long distance to cover before we reach my main body," added Mini-Katsuyu. "I wouldn't recommend staying out here in the open when night falls, so you should probably get going. Here, let me get you a guide…"
Mini-Katsuyu's flesh rippled, and an even smaller Katsuyu emerged from the top of her head. Micro-Katsuyu's eyestalks waved back and forth as if to say hello, so Sakura gingerly picked up the hand-sized slug and placed her on her shoulder, just like a pirate's parrot.
"What comes out at night that's so scary?" asked Sakura as she ran, following Micro-Katsuyu's directions. "Some kind of giant duck that eats slugs?"
Sakura could scarcely imagine what kind of monstrous predator could devour slugs the size of lorries.
"Not at all, you misunderstand!" Micro-Katsuyu giggled in her ear. "Shikkotsu Forest is probably the safest of the three great Sage Regions, but it gets awfully cold and damp at night here. We wouldn't want you catching a cold, would we?"
As they continued their journey through the ancient forest, Micro-Katsuyu started explaining why Sakura had to be brought to Shikkotsu Forest. Unlike the toads of Mt Myōboku, who took an active interest in the affairs of the shinobi world, the snakes of Ryūchi Cave and the Katsuyu of Shikkotsu Forest mostly kept to themselves.
Because of that, these two Sage Lands had no use for something like the toads' summoning contract scroll. The only rule in Ryūchi Cave was the law of the jungle: the White Snake Sage and the three Snake Princesses would rarely take the initiative to order around the lesser snakes in Ryūchi Cave. If a snake wanted to forge a contract for fun, for food or for any other reason, it was up to them. As for Lady Katsuyu, she was the only slug in Shikkotsu Forest, so she naturally did not need a contract scroll to keep track of any subordinates and their summoners.
As such, before Sakura obtained the right to summon any of Katsuyu's divided selves, she would need to be brought to Katsuyu's main body to be properly evaluated. As for learning Senjutsu… Lady Katsuyu hadn't mentioned it yet, and Sakura wasn't supposed to know about it yet either— but she was already thinking of a way to bring it up.
…
Katsuyu's main body was so enormous that it didn't seem to grow any larger as Sakura approached, even after two straight hours of running— though it was hard to tell through the dense canopy overhead. But an hour later, a few minutes before sunset, Sakura finally managed to reach her destination at the foot of Mt Katsuyu: a pulsating wall of slug flesh. Ew.
"I'll handle conversation," said Micro-Katsuyu, as Regular-Sized-Katsuyu lowered one skyscraper-sized eyestalk to gaze at a frozen Sakura. "My main body could blow you away with one whisper from her mouth."
"…and I'm very grateful for that!" Sakura spluttered.
For a few seconds, Katsuyu stared at her in silence, the beady eye atop its eyestalk unblinking— making Sakura incredibly uneasy.
"Good, you've mastered the Yin Seal," said Katsuyu appreciatively. "Okay, I acknowledge you. From now on, I will respond to your calls, Sakura-san."
Sakura blinked.
Was it seriously that easy? She wouldn't have to prove herself, or give her anything in exchange for services rendered?
"Of course, if you have any questions, I'll gladly answer them," continued Katsuyu. "Or if you want to go home, I'll teach you how to Reverse-Summon yourself right away."
"Why ask about the Yin Seal?" asked Sakura timidly. "What would have happened if I hadn't mastered it?"
Katsuyu let out a soft, pleasant hum.
"It makes me ever so happy to know humans are still using the technique I created so long ago," she said gently. "But I would have made a contract with you either way. Lady Tsunade believes in you, and that's more than enough for me."
"You invented the Yin Seal?" said Sakura in surprise. "How long ago was that!?"
Sakura had always believed Tsunade to be the Yin Seal's creator, but apparently, that wasn't the case. The original Naruto story had never delved deeply into Tsunade's association with Shikkotsu Forest, leaving the details shrouded in mystery— not that Sakura had ever given it much thought.
"I was a young girl of about your age when I first came up with the idea," sighed Katsuyu, reminiscing fondly. "It was a few hundred years before that Sage of Six Paths fellow started spreading chakra to the humans. Yes, I do believe it was around then."
'No wonder she's so huge!' exclaimed Inner Sakura. 'She's been growing nonstop for thousands of years!'
And Sakura had just found an excuse to bring up Sage Mode!
"The Sage of Six Paths, the three Sage Regions, Jiraiya the Toad Sage…" Sakura took a deep breath, steadying herself. "I've been hearing those terms for a while, so I've been wondering… What exactly does it really mean to be a Sage?"
Regular-Sized Katsuyu let out a low rumble, triggering a localised tremor that nearly knocked Sakura off her feet.
"Oh dear," said Katsuyu fretfully in Sakura's ear. "Lady Tsunade asked me never to bring up the subject around you, but she didn't say what I should do if you were the one to ask…"