The tracker they get him is particularly good for this dungeon: they're an S-ranker from Norway (or, well, Korea classifies them that way, Norway itself doesn't use the rank system) who can conjure a path made of solid light under their feet leading to their destination. That makes it very useful for navigating the insanity of this place since they don't have to rely on the existing terrain which is often very misleading or unreliable.

Oh yes that is a very useful power.

However, they're going to need something that belongs or recently belonged to their target, or some other way to uniquely identify them.

...would a picture do?

In a pinch.

Ok hang on he still has the door code for Si-yeon's place so he can teleport there and back with something of his in less than two minutes.

Oh! Yes excellent that works perfectly.

Woo-young will teleport them to Si-yeon and Chun-hee's last known location, then.

The tracker uses their power, their solid light conjuration stretches away from them in a specific direction and then...

...vanishes into thin air.

Yeah, that's what he fucking thought.

"They got pulled kata or ana," Tae-gun says into the comms. "Min Woo-young, if we stand here at their disappearance point, can you teleport us in the right direction?"

"—yes, I think so." It might be really costly but their best model of this dungeon has it as actually really thin along the fourth dimension such that teleports along it are actually pretty easy. It's of course approximately impossible to know exact scales but their best guess is that it's less than 10cm "tall".

Alright. He goes to the spot where the path disappears, gets a little radar doodad to generate a map of the 4D surroundings—

"—found them."

Vworp.

They're in hot fucking water, pun unintended. Chun-hee is holding up a bubble of water as a shield around herself and Si-yeon—

—except Si-yeon is vanishing into thin air and reappearing at irregular intervals, looking incredibly harried.

Whenever he appears Chun-hee shouts instructions, to get around some of his backlash and get him focused on the fight, but it's really hard to fight something in four dimensions.

To give an impression of how hard it is, let's take this analogy back one dimension down. Imagine you're looking down at a little sapient dot on a flat piece of paper. That little dot is surrounded by a circle that it thinks is a perfectly protective forcefield—after all, there is no direction it can perceive that it can be assailed from. So then you go and you poke a hole into the piece of paper with your finger, from the dimension the dot just cannot perceive, and there's nothing it can do to resist you.

Unless it can figure out how to step out of the paper, too.

Ha Si-yeon's power is that he can do things. Therefore, today, he can move in four dimensions. That is a thing that one does, and he can do things, therefore he can do that.

(It turned out to be surprisingly backlash-cheap, too! Not the cheapest but it seems that, as far as his power is concerned, if he is in four-dimensional space, there shouldn't be much of a difference between being able to fight well in 4D versus being able to fight well in 3D. The main problem is his senses, but he's working around that.)

However, he's still been in this fight for fifteen minutes, now, and fifteen minutes of uninterrupted power use is. A lot. It's a lot.

The little dot on the piece of paper doesn't really have a way to properly understand what you are. If it manages to step out of its piece of paper because of magic bullshit, it'll still only be able to properly interact with two-dimensional cross-sections of you.

By a similar token, it's really difficult to understand what exactly in the everloving fuck they're fighting. It changes sizes in place and disappears and reappears in other places as it moves around in a dimension you just can't see. It's—blobby, and smooth. The three-dimensional cross-sections it projects onto the area visible to them never get bigger than a person, but it's hard to make out any kinds of detail.

...this means that everyone here other than Si-yeon is a liability. Chun-hee's water shield is completely ineffective, and a waste of backlash. However, the monster engaging them so actively means that the core is probably here. Just—

"Sunbae, status?"

Oh, right, the relay worked.

"Si-yeon can fight in 4D, Kim Chun-hee is telling him what to do, get this radar pulsating and find us the core so Si-yeon can kill it."

Oh thank goodness someone found them.

"Roger that."

"Hyung, pull me kata." Two separate 3D projections is—still not perfect, especially since Tae-gun can't even rotate properly in 4D or move on his own, but whenever he sees the thing's projections he can harass them and that'll be extra pressure that just a single person can't provide.