Shirou in Another World.

Volume 2.5: Interlude 1

Learning how to navigate was easy.

You pick a direction, use it as a reference, then go in the direction you wanted.

The Space-Time Continuum had no direction. It was either you moving, or not. There was no direction, only reference points in the form of the dimension you aimed at.

Shirou, in all his intellect- knew that he lacked the ability to learn directly under Zelretch.

So, he cheated. As was expected from the faker.

One traced noble phantasm later, and Shirou was jotting down notes while Zelretch taught him. At the same time, he was also summarizing and simplifying them to process in his original state. One day in the future, he could learn to use the knowledge without the assistance of an intellect boosting noble phantasm.

But for now, Shirou was not beyond cheating.

After all, traversing the Space-Time Continuum required an understanding of Causality, Time, and Relativity.

"What do you know about Causality?" Zelretch asked him.

Causality, wherein all events directly or indirectly influence one another.

"All events have causes which allow them to occur. These events also produce effects that allow others to come into fruition. Some materialize, but also the inexistence of an event could be directly tied to one event not producing the correct outcome."

The Wizard Marshall nodded.

"Using Causality, why do you think dimensions do not come into contact with one another?"

Shirou recognized the connection right away.

"There is something keeping dimensions isolated from one another."

"Correct. Most dimensions stay independent of one another. Intersection, or any form of connection between major dimensions like the one you're on...is extremely rare."

Causality, wherein other Space-Time factors contribute to the effect of another Space-Time event. At a certain point, some dimensions create massively larger effects on the field around them, sending ripples out that affect other dimensions nearby. Think of it like a large cruise ship, forcing privateer boats to veer away to avoid smashing into contact with it. The same happens with dimensions. They are stable independent Space-Time events that avoid encountering one another to retain that stability.

Shirou's Unlimited Blade Works was like a small jet ski floating around in a massive ocean of cruise liners. Unless he forced his reality marble to attach to one branch of the World Tree or to approach one of the bubble dimensions, he would forever float in between spaces to avoid the collapse of his world.

One of the main reasons Zelretch paid attention to this branch of the World Tree was because of the intersecting Man and Fae realms. All the realms were connected to one twig, something that was common for one self-contained universe. For this one, it was like two leaves merged at a certain point.

"Wait...this one is special?"

Shirou wasn't aware of the history of the current world. Much less time for learning outside of work during his tenure in Akatsuki. Hearing about this dimension's uniqueness made him more nervous with Zelretch hovering in the background.

But...that wasn't going to stop him.

"Have you heard of the Fae Realm?"

Shirou recalled what he read about the history of the world. Unlike the other races, apart from the Phantasmal Beasts who originated from the same land as that of Man, The Fae stood out for being the most renowned. They were particularly active in the Britain Isles off the west coast from the middle continent. Though, that was because most of the information came from the famed Albion Isles.