[X] Investigate the outer slopes of the cavern. In the very least the circular route will provide you an opportunity to observe the pit from different angles, and may revel a path hidden in one of the shadows.
Wiping away the tears in you eyes, you duck underneath the cave's mouth and begin hiking down. Despite the lack of a trail and relatively steep incline your passage is both quick and balanced: In a minute you're already halfway to the sinkhole, the various footholds and some nimble footwork more than enough to carry you safely. But even with you eyes only half-adjusted to the gloom you can see that the terrain becomes increasingly treacherous the closer it gets to the pit.
Stopping your descent almost two-thirds of the way down you take a good look around the chamber. Hiding among the many stalactites hanging from the ceiling you can see a small hole almost directly overtop of the pit. Though it's barely illuminated this late into the afternoon, you can tell that it's situated perfectly to allow a noon-day sun to shine down into the chamber. The ground to either side of the hole extends significantly further than that directly opposite from you, to your left sloping into a shadowy crawl almost flush with the cave's roof whereas the right-hand side stretches at least half a dozen meters before your vision's obscured by a curtain of stalactites. Straight ahead there's a good several meters between the sinkhole's edge and the wall, but whatever spare space there was between them has been taken up by a miniature mountain range of stalagmites. Close as you are you still cannot see the pit's bottom from where you stand.
In no rush to test any of the terrain skirting the sinkhole's edge, you decide to practice some caution and move in a vaguely circular path around the room. Presuming everything goes right you expect to be standing in roughly the same spot after just a couple of minutes, if not wiser for the effort then at least with some of your cautious curiosity satisfied. As you move to your left you need to slow down and watch your step when you pass over the first tangled cluster of roots and vines, their precarious footing almost leaving you feeling as if they're trying to tangle your feet sometimes. Partially climbing the northern wall afterwards reveals that its crawl goes far deeper than the dim lighting can penetrate, a blind grope of your hand finding its stone solid for at least a good two-thirds of a meter in. Just how deep into the mountain the cleft runs is be impossible to tell without coming back at another time with a portable light of some sort.
As you start climbing back down the north wall's slope, a modestly sized chunk of stone dislodges underneath your foot. Fortuitously for you it's the only stone that breaks away, cascading with a stream of pebbles towards towards the center of the room along with the end of a root that had been previously been buried beneath it. You can hear the cobble crack as it strikes something hard past the lip, a rattling sound echoing within the cavern for several minutes as smaller loose rocks pitter-patter over the side. While you still feel confident in your footing, the incident serves as a good reminder that this cave has a deservedly bad reputation in regards to safety.
The remainder of your lap passes without any significant discoveries or events. Besides the narrow ceiling shaft and the squeeze raised within the northern wall you find no additional entrances or exits connected to the chamber. The various roots and vines continue to defy all attempts to define where they begin or end, and if anyone or anything occupied the cave recently they either passed quickly or were quite thorough in leaving no evidence behind. You have no choice but to double back for some supplies from the dojo if you want to investigate this cavern further, but at least now you have two possible leads to-
"Hello?"
You pause mid-train of thought, unconsciously holding your breath. Was that a trick of your ears just now? Or of the wind whistling outside? It almost sounded like-
"Is someone there?"
No. It's not your imagination. Someone's calling out, and from quite far away by the sound of it. But where? The echo doesn't have the right ring to be coming from outside, and if the cleft was labyrinth enough to blot out any light they brought with them there's no way you should be able to hear them from all the way over where you're standing. The noise must be coming from down the pit. But then why didn't they call out earlier?
What will you do? Outside moving precariously close to the sinkhole's edge there's no way you'll be loud enough for them to understand what you're saying. You could just make a lot of noise to let them know you're in the chamber above them, or you could stay quiet and wait to see if it's you they're calling out to. Or you could ignore the voice entirely and leave, either doubling back for supplies or looking for another cave to continue your investigation from.
[ ] Approach the pit's edge and call down to the voice's owner. After your investigation you now know where to and not-to stand along the precipice, and it will be easier to communicate with… whoever, if you can both understand one-another.
[ ] Make enough noise to be heard. Whoever is down there, you're not about to stick your neck out for them just yet. You are, however, willing to let them know the chamber above them is occupied.
[ ] Remain quiet. If the voice's owner joins you in silence then it's likely they had nothing of importance to say. Meanwhile, if they keep calling out, you'll know soon enough who they're talking to and why.
[ ] Leave the cavern, continue exploring the mountain. You are here to see if there's any truth to the rumors, and if so search for remnants of Ōgai's tōki. People at the bottom of ditches are not of your concern.
[ ] Leave the cavern to return to the dojo. You are here to see if there's any truth to the rumors, and if so search for remnants of Ōgai's tōki. If the voice's owner is still there by the time you've come back with a rope and spikes then you'll deal with them then.
[ ] Write-in.