Greater Grail

Shirou took the first step, and connected to the Greater Grail through
the ‘thread’ he’d made while establishing a prana supply connection—

Instantly, his world turned upside down.

His existence was instantly fused with it. He was overcome by a comfortable feeling like when one is about to fall asleep, and the
sensation continued infinitely. He was engulfed by something soft, and kept sinking without end—down, down, down.

Any malice, no matter how strong, would vanish here.

Any desire to kill, no matter how great, would be useless in the face of this.

This entire space, filled with happiness, peace, pleasure, order and purity all mixed together, felt like sweet milk dripping over his entire body.

His brain’s functions halted.

His brain’s functions became unnecessary.

Thought and instinct are unneeded. So melt away. Melt away and become one with it, until you’re reduced to mere sweet, formless milk—

“…You’re in my way.”

Shirou rejected that supreme pleasure with extreme ease. He scrunched his face at the great pain that ran through his arms, but he felt relieved at the same time.

Shirou had touched this several times while linking with the Grail to connect the prana supply. He had clearly understood from those brief touches that he would likely become unable to think of anything and merely dissolve into it if he plunged his entire body into it. To prevent that, he’d made his arms feel pain. The reproduced pain came from the despair which he’d experienced in the past—and his black rage which sought to overcome it.

[...]

No matter what wish it was asked from the outside, the Holy Grail would grant it all. Then, if Shirou asked it to ‘save humanity’ from outside of it, would the Greater Grail bring about that salvation?

—Of course, the answer is no.

The Greater Grail can’t do what’s impossible. That’s why Shirou was risking his very life to invade the Greater Grail. He had a wish that was impossible for even the Greater Grail—in that case, he merely had to overwrite its system from the inside and forcefully make the Greater Grail grant it.

He was attempting to adjust and reprogram the Greater Grail itself, something that would never be allowed in a normal Holy Grail War.

If it wouldn’t grant his wish, then the Holy Grail was the one that was mistaken. So he would merely correct it.

Shirou walked towards what he had long sought—which surely lay beyond this expanse.

***

Several hours had already passed since Shirou had dived into the Greater Grail. He would probably require an even more considerable
amount of time to complete his task. The Greater Grail was a work of art on the level of the divine, and Shirou was trying to modify it from its very foundation. There was no way he would finish quickly.

For the time being, Caster had returned to his study and resumed writing. It was then that he received a telepathic message from Assassin of Red.

“Caster, has Master already dived in?”

“Yes. Have there been any changes to his prana?”

“No. There’ve been no changes to the prana being supplied to us and the prana accumulating in the Hanging Gardens from him. I suppose this means that, even if the interior of the Greater Grail is another world entirely, the Line connecting Master and Servant can’t be severed so easily"

Shirou had been most concerned about the moment he dived into the Greater Grail.

If his link to the rest of the world was cut off, everything would immediately fall apart.

“In that case, I shall continue with my writing.”

- Vol 4 Chapter 4