The group that arrived at the oasis south-east of the Mukade Cliffs was utterly spent. Xavier and Sumiko had both largely escaped injury, but Kahina and Yukio had suffered multiple bites from the smaller centipedes that had become inflamed as they walked. Kahina in particular was in bad shape, stumbling along the last few miles in a feverish haze to collapse where she stood when at least they made it to the oasis. Yukio being not much better, Sumiko scouted out the surroundings while Xavier struggled to fill their canteens with water.
The oasis wasn't much to speak of. Xavier had been under the vague assumption that an oasis necessarily included a sumptuous, clear-water pond with lush trees all around, but this one was barely more than a small, silty spring of water surrounded by clumps of low-lying underbrush. Xavier just hoped he didn't contract some weird parasite from drinking this stuff; he'd have to ask Sumiko if they needed to boil the water or similar before drinking it.
Sumiko returned to pronounce the surrounding area seemed quiet and safe, and after working their way through some of their dry rations and doing their best to dress Kahina's and Yukio's wounds the small party sprawled out on the sand and fell into unconsciousness.
The next day neither Kahina nor Yukio was in any shape to travel, so Sumiko reluctantly decided to spend another day at the oasis. While the rest was nice, there was nothing to do. Xavier explored the nearby area, keeping close to the borders of the oasis, but aside from spotting a couple of lizards and some normal-sized bugs there wasn't much to see.
Despondent, he wandered back to the area where they had made camp, at which point Princess piped up. "I don't think your giantess friend is doing so well. Why don't you wander over that way? I may have a solution to your Vigor blindness."
"Vigor blindness?" asked Xavier, as he trudged toward where Kahina lay sprawled between two of the larger bits of undergrowth in the area.
"Yep. I've been trying to figure out why you're so oblivious to the world around you, although if your story about originating in another reality is true then that explains a lot. But anyway, by all rights you should be even more Vigor-sensitive than your animal friends, and I think we can solve that hang-up with a little work. And maybe help Kahina in the process."
Xavier knelt by Kahina. «Kahina-san, Princess thinks we might be able to help you. Do you mind?»
Kahina just grunted in response. He tentatively felt her forehead and she was burning up.
"I really hope you're right about being able to help her," he muttered to Princess.
"Let's give it a shot," said the mononoke. "For the moment, I just need you to look at her. Can you tell where she's been bitten?"
"Uh, I mean I know where a few of the bites are from last night, but how would I be able to tell where all of them are without looking under her clothes?"
"Eh, just keep looking at her. Okay, anything? Now? No? What about now? Damn it." Princess shifted the vine she always held against his head, and wrapped another one around his forehead to come to rest near his opposite temple.
"Princess, what are you—whoa!" Suddenly, Xavier's vision swam. "Don't screw with my—wait, what the hell?" For a brief moment, his vision stabilized, and Xavier could see something emanating from multiple points on Kahina's body. It wasn't light, and it wasn't heat haze, but it was sort of like both those things.
"Hmm, maybe not," muttered Princess, and Xavier's vision snapped back to normal.
Xavier grabbed Princess's stalk, pulling her off his shoulder so he could look her full in the flower. Her vine fell off his forehead. "What the hell did you do? Are you messing with my brain?"
"Oh, that worked? Excellent! And that wasn't anything that will hurt you; I shoved your internal Vigor around a little bit, but it's perfectly safe. Well, you know, as long as I don't do it too often or too long. Which I totally won't, because I'm very responsible with other people's squishy bits."
"I don't even—fine. So what was the point of messing with my—you know what, I'm not saying that, and you shouldn't, either."
"Mammals," grumbled Princess. "And the point is to get you to learn to do that yourself. Now that I've got a sense for what we're looking for, we can get on with the real work!"
Over the next several hours, Xavier and Princess played a weird game of hot and cold: Xavier would try to recreate the feeling he'd had when Princess messed with his head, and she'd tell him if he was getting close or not. It was incredibly frustrating, and Xavier never was able to quite recapture the ability to see Vigor on demand, despite Princess forcefully messing with his head a couple more times to show him what he was aiming for. On the plus side, there was absolutely nothing else to do and over the course of their fruitless attempts Princess also coached him through intentionally drawing out some of the Vigor from Kahina's numerous centipede bites.
"Those centipedes really were tiny youkai," Princess commented at one point, as Xavier focused on drawing Vigor out of a bite faster than usual. It was a bit like sucking in his gut without using any muscles. "Normal poisons are just chemical reactions, but this one has a pretty vicious Vigor-based component driving it, as well."
"Is that unusual?"
"That many miniature youkai in one place like that? Yeah, that's not normal. There's something seriously weird about the whole area. I'm just glad we didn't try to enter the actual cliffs. There was a huge source of Vigor somewhere in there."
"Bigger than that monster that took out the Sundlin soldiers?"
"That thing? I didn't even notice it until it started moving. Lost in the background noise."
"…let's never go back there, ever," said Xavier with feeling. Nope, he wasn't tripping any flags, not at all. No sirree.
Eventually, Xavier finally succumbed to his budding headache and Princess let him drink some water and rest while the sun did its best to burn the life out of everything beneath it.
The next day, Kahina and Yukio were feeling good enough to move, and the party set out walking. Along the way, Princess kept Xavier practicing his ability to sense Vigor.
By the end of the day after that, Xavier was thoroughly sick of getting bossed around by a plant, but he was also able to sporadically see emanations of Vigor when he tried. Princess told him he was doing great in a tone of voice that conveyed the exact opposite, and he did his best to shrug her off his shoulder to her intense annoyance.
At the end of the third day since setting out from the oasis, they finally found their way to the small bakuhito town of Yonaharu.