Perhaps I should rewind a little, back to our conversation in the library within the basement of the Scarlet Devil Mansion.
"Why would you ask me about that?" Patchouli asked in response to Renko's request.
Renko leaned forward across the table, a mix of excitement and cunning playing across her face. "Because it just so happens that you are the only one I can ask, miss Patchouli. With the balance of power as it currently stands, both the Child of Miare and the youkai sage wouldn't be likely to give me straight answers if they give me any answers at all and the tengu are so afraid of the possibility of ever seeing an oni again that they might kill me just for asking. You are the only person I can think of who is in the lucky position of fulfilling all three of the necessary criteria: You're interested in the Underworld, you're a youkai, and you're not directly involved with the sage's plans to maintain the status quo. In addition, your predilection for collecting a vast and all-encompassing knowledge of the world means you're both likely to already know of an entrance to the Underworld, and eager to find out more."
Patchouli looked up at Renko as she leaned across the table, glaring as she huddled deeper into her lavender robes. "I can't guarantee I know such a way. The denizens of the Underworld are supposed to be sealed such that they can never return, so the path is sure to be blocked up or guarded. Even if I were to show you what I know, there'd be no way for you to use it."
"I don't believe that, miss Patchouli. After all, Suika Ibuki is here on the surface with us now. She's what got you interested in the Underworld in the first place, isn't she?"
"That doesn't mean anything. Suika came up but any seal she broke could have been patched long ago, and you're not Suika. How do you know that she wasn't just able to get here because of who she is? She might have come up through a tiny crack as a mist, or gotten past a dangerous guard with her strength."
"That doesn't make sense either, I'm afraid. Suika had been down in the city of the Underworld for a long time. If all it took to get to the surface was the ability to fit through a small crack I'm sure any number of other creatures could have come up before her. Those earth spirits, for example don't sound like they'd have much trouble with it, but they've stayed sealed down there until now. Similarly, if the way were guarded, then someone would have seen her leave. Even if she had gotten past them, that means that someone probably would have come after her to try to drag her back, don't you think? No, the only sort of seal that makes sense is one that would have been exactly the sort the youkai sage would have been most skilled at putting in place. A barrier of some kind. And when it comes to getting past barriers, well you can't beat Merry's eyes. If you show us the way down, I have no doubt that she can find a gap in any boundaries down there."
"Renko! Don't volunteer me for this crazy scheme without asking!"
"Come to think of it you did bypass the wards on Flandre's room didn't you? Hmmm."
I had opened my mouth to scold Renko further, but upon looking across the table at the way that Patchouli was already appraising me, I found I lost the will to speak.
"Miss Patchouli, you've been wanting to find out more about the Underworld since the Incident with all of those parties, haven't you?"
"Yes..." she muttered, looking at me in a way that felt like she was staring straight through me.
"That was quite a while ago. The fact that you are still interested in what's down there suggests to me that you've never tried going there yourself though, correct?"
"That's right. Even trying would be enough to bring Yukari's wrath down on me. It's not worth the trouble, no matter how curious I might be."
"You have my sympathy, miss Patchouli, I can only imagine how frustrating it might be to be looked upon as Gensokyo's most learned scholar, a veritable personification of the concept of knowledge, but to be bound to uphold the very thing that prevents you from learning more. That must be a terrible source of regret for you."
"Yes..." Patchouli muttered looking down and biting at her thumbnail. "It is rather vexing. Despite all that could be learned, the laws of this world prevent me from investigating the matter..." Suddenly she froze in place and her eyes went wide. She looked up at Renko, who was already looking back at her with the same eager expression she now wore. "The rules of the non-aggression pact prevent any youkai from the surface from travelling to the Underworld..." she said.
"...but they don't say anything about human travelers," Renko added, completing her sentence. "And if you had a human investigator who could go down for you..."
"Then I could use them as my proxy to learn all I liked about the Underworld myself!" Patchouli rose to her feet, her chair scooting back from the table as she did so.
Renko practically leapt across the table, lunging as far as she could to take hold of one of the magicians hands with both of hers. "Miss Patchouli, infiltration, investigation and information gathering just happen to be the three specialties of the Hifuu Detective Agency. If you really want to know more about the Underworld, then I highly advise you to engage our services. The mission of our agency is to reveal the hidden secrets of the world!"
Patchouli stared up at Renko for a moment with a stunned expression on her face, then broke into a fit of dry coughs. Shaking her hand away from Renko's grip, she took a sip of tea then caught her breath. "No, no. It's utterly ridiculous. Sending you down there would be acting within the letter of the law, but violating its spirit would still be sure to incur Yukari's wrath."
"Well, that's debatable. Or it would be under normal circumstances anyway. In light of the current situation with the geyser, there are already denizens of the Underworld that are making their way to the surface. It would be difficult, I think, to make the case that someone from the surface sending a human down to investigate why and speak to whoever's in charge down there about it would be intentionally violating the treaty. If anything you'd be working to maintain it, and staying within the bounds of the agreement to do so.
"Going down there at all would be a violation of the treaty. If you were going down as my proxy, that'd be just as bad as me going."
"Precisely why you should show us the entrance and then pay us for any information we find. If you don't explicitly give us a commission to go down, you maintain plausible deniability. What's more, the treaty was signed by the youkai sage acting on behalf of the youkai of the surface and the youkai of the Underworld, right? Humans aren't even a party to the treaty. We have free reign to look about all we like down there! If we should happen to uncover information of interest to you and sell it, well that's not political interference, that's just business, right?"
-.-.-.-.-
-And so now you see how Renko's follies had compounded, one atop the other until we were left here.
"Back when the oni left for the Underworld, they have to have used a passage large enough to allow a caravan of significant size to pass through it. As far as I know this is the only opening in the ground large enough to be a candidate. I can't guarantee that it leads to the city of Former Hell, but given that there are vengeful spirits coming out of the geyser at the Hakurei shrine, I think it's safer to send you down here than to try and dig up a passage there. So. Will you be going then?"
As always, Patchouli's tone was completely disengaged, sounding like she couldn't care less which path we should choose, and with little expectation of our success. The mere fact that she had not only brought us here but come with us as well suggested otherwise, however.
"We should have called Sanae before coming here. Maybe we can go get her then come back tomorrow, Renko," I said, secretly hoping that I might talk her out of this plan in the time that would take.
"No, I'd like to not get Sanae involved in this one. As a representative of the Moriya shrine, having her moving into the Underworld could have unintended political consequences. Besides, she and Lady Yasaka seem pretty busy just now, I don't think she'd be able to come if we called her."
"Well, I won't force you to go. The whole idea was a longshot to begin with." Patchouli said wheezily.
"No," Renko said, rising up from the ground and dusting off the front of her shirt. "The Hifuu Detective Agency has taken the case, and I intend to deliver what we can. This is just an issue of logistics. I'm sure between the three of us there's something we could figure out. Is there some kind of magic that could get us safely to the bottom, miss Patchouli? You teleported us this far without issue."
"Teleporting to a place you've never been is much harder, and harder still if you're sending someone other than yourself. I can try it if you like, but how do you feel about being buried in several hundred tons of rock or materializing a few hundred meters above the bottom?"
"Eugh, I'd rather avoid that. Would it be possible to conjure an extremely long rope ladder or the like?"
"That's not how it works. I can't create something from nothing. If we already had a ladder I could call it here, or I could summon a demon and make it take the form of a ladder, but I'm not in the mood to pay a contract with any more of my power, so I might have to take a dozen years or so off of your lives in exchange."
"Ah, no, that's not a great option either then. I don't suppose you'd be willing to just fly us as far as the bottom and just drop us off then?"
"If I could do that much, I could investigate this myself. Going down there might well be counted as a violation of the treaty. It doesn't explicitly specify what the border between the surface and the Underworld is supposed to be."
Renko sighed, rubbing at her head. "Well, I guess we'll have to go get Sanae then. I don't know how to rock climb and I don't think we could find a rope long enough to safely lower ourselves down."
"Even if you could, people have to train to go down holes on ropes, Renko." I interjected. "If you try to go down there by any means other than flying you'll die for sure. You might not even die instantly if you end up with two broken legs at the bottom of the shaft, waiting to die of thirst."
"Sheesh, thanks Merry, that's real encouraging. I don't think I'm about to sprout wings any time soon though."
"Then give up, Renko. Even your recklessness can't defeat gravity. You'll have to find a way to survive the disappointment of not getting to throw yourself into Hell."
"I'm not a taxi service," Patchouli said grouchily. "If you can find your own way down, I'll pay for a report on what you find down there, but I don't do delivery. Can you at least find your own way home from here? I'd like to go inspect the shrine."
"We'll manage." Renko said. "I think I can see the mansion through those trees."
Patchouli grunted in acknowledgement and floated off of the ground, turning towards the Hakurei shrine. She seemed about to fly off, but then stopped and turned back to Renko.
"Oh, I should ask you one thing more. To summon the Administrator's shikigami, you need fried tofu, correct?"
"I'm not sure if I'd call it a 'summoning' exactly, but she'll often pay you a visit if you leave some out." Renko said, grinning.
"Very well. I wonder where one could get such a thing."
"There's a tofu shop in the village that will sell it to you."
"I'll have Sakuya pick some up then." She said. Without another word or moment's consideration for our predicament, the magician left, departing to the east.
-.-.-.-.-
Left to our own devices as Patchouli flew off, Renko looked down into the hole again. "No doubt about it, Merry. We'll have to find another collaborator."
"In theory, shouldn't Ran be watching us right now? We are outside the village after all."
"Probably, and I'll take the fact that she hasn't shown up to warn us off as proof that the youkai sage doesn't consider this plan a violation of the treaty. I would expect she's rather busy though and wouldn't take kindly to us asking her to fly us down there. Besides, she's even more bound by the laws of the treaty than Patchouli would be. What we need to do is find another human who could bring us down to the bottom. Ideally someone who isn't tied up with any faction with a stake in maintaining the non-aggression treaty."
"That would pretty much have to be Marisa, wouldn't it?"
"Yeah, probably. She'd likely be interested in the idea, but I don't know if she could fly us both down and back up on that broom. Maybe we should talk to the kappa. Do you think they could invent some kind of technological solution? Like a cable elevator or a helicopter or something." While Renko mused she absentmindedly kicked at a clod of earth, dislodging a half-buried stone and propelling it over the edge of the pit.
"Renko! Don't kick things in there, it's dangerous!"
There was a sharp thud as the section of earth Renko was standing on abruptly shifted a few centimeters downward. "Huh?" Renko said stupidly, looking down at her feet as she attempted to regain her balance.
I lunged forward. I saw my fingers weave between hers as we heard the rattle of gravel crumbling away. If this had been a fictional story, some action movie or adventure tale, then what would have happened is she would have been left dangling by one arm as the ground collapsed and I scrabbled for purchase. Renko would have hung out, suspended over the abyss in a thrilling and tense scene while I tried to haul her up with one arm. Somewhere, Sanae would have been watching, cheering me on.
Reality was much different. My fragile arms could never suspend the weight of an entire person dangling off of them. Moreover, in lunging for Renko I had already shifted my center of balance forward and thrown my momentum toward her. My body had foolishly expected the ground beneath my feet to support me and in rushing to her I had stepped forward onto the same ledge she was standing on. If I had had time to think about it I might have realized how foolish that was. Even if I had though, I think it might not have changed things a bit. Even if I had all the time in the world to plan, I can't imagine choosing to stand by and watch helplessly as Renko fell.
And so what happened was not either of us twisting in the air and grabbing the edge of the pit with our fingers as we fell, or snagging our clothes on a precipice and crawling out or landing in the canopy of an oh-so-convenient tree growing horizontally out of the edge of the chasm. No, all that I accomplished was pitching myself forward and grabbing Renko's hand, imparting a momentum that sent us tumbling end over end as the ground gave way and we both plummeted into the fathomless blackness of the shaft, making inarticulate screams that were not even words.