You decide that checking in with the Administrator of the War was a good idea; it's help Shirou further understand what exactly he's in for, and lets you figure out how safe this 'Neutral Ground' is. It might also give you some more info on how the Grail works besides 'grants wishes', because those fuckers always find a way to shaft you. 99% of the time you wish'll go FUBAR and then your life goes down the crapper. Hell, the only reason you still hold onto that Luck Blade is because you never know when things have gone so far off the deep end that a wish that'll probably fuck up is the only way to make things better. When you have literally nothing else to turn to, and it's better to risk it then watch things get worse.
You've never been in that sort of situation; yet, at least. But you know it's going to come eventually; so it's best to be prepared. And hey, maybe that wish will be the 1% that doesn't fuck you over. It could happen.
Regardless, it's time to actually act instead of ponder; "Hey Shirou, let's go meet the Administrator of this whole thing and get registered, or whatever. The weird info download that taught me all this stuff was sorta vague on that. Besides, we can see how well protected this 'Neutral Ground' is."
Shirou nods, "Right, let's go." With that, you both enter the church, ready to meed the guy making sure that nobody screws the pooch and ends up causing a hugeass incident that can't be covered up.
The moment you walk in; you realize it. 'Evil Lair. Fucking Evil Lair. Holy Shit is this one helluva Evil Lair'. Well...that answered that question. Oh yeah, the Grail; so not worth it. And probably a total trap. You then notice the Administrator; mullet, dead eyes, a grin that's more fake than a two dollar elf whore, off-kilter vibe that makes you feel edgy: the man's completely fucking evil. Irredeemably so; he's probably behind this whole mess. Right then, at least you knew who to kill once you dealt with everyone else.
Then the fucker speaks, "Ah, hello there; I presume that you are a Master participating in the Holy Grail War, along with his Servant?"
Holy Crap, he even sounds evil; how does he get away with even existing! Alright then; looks like it's time to begin some verbal warfare, the best kind of warfare. Subtly casting a Glibness spell on yourself, you begin to bluff to the man, "Yes, I am Servant Saber, and this is my Master; Elfanderel von Lichtenstein. He is a great Lord of Magi, ruler of all that is mystical in Western Europe. He's participating in the war to get revenge on the Emiya clan for killing his grandfather, Lord Karnavash. We were hoping to verify our place in the Holy Grail War and make sure we were clear on what is and isn't permitted. That is if you weren't busy Mr..."
"Ah, my name is Kotomine Kirei; and it is an honor to have a magus of such high social standing participating in the Holy Grail War. Now then," he turns to Shirou, "What questions do you have, Lord Von Lichtenstein?"
"Um...this church, it is Neutral Ground; correct? What exactly prevents Masters or Servants from attacking here?"
"Ah, that would both bring the full force of the Church upon them for violating the terms of our supervision; as well as potentially destroy the Grail, for it is here that it is rewarded to the victor." Bullshit, you can tell that there's something he's hiding. Oh it's hidden; the part about the Church and the Grail were mostly right, mostly. But you can tell he's hiding something about the Grail itself.
"Ah, My Lord; if I may ask, do you not have any other retainers? I would assume one of your stature wouldn't travel alone." For a moment, you thought Kotomine was calling your bluff; except that from what you can tell, he was genuinely curious. He totally bought the whole story, not even questioning it. You...you never bluffed this well; bluffing needs you to constantly keep the target on their toes, while also keeping them grounded enough that they don't think you're full of shit. And Kotomine doesn't look nor seem like the gullible sort, so what gives? I mean, it's not like you're some super...
...Wait. You were some sort of super being. Immediately, the Grail fills your mind on what parameters are and how they compare to a regular person. It was...staggering. Man, you were near the levels of power you had as a Demi-God, but without all the obligations and duties. Awesome.
Oh, right; this guy. Well, since you can officially get him to believe anything you say as gospel from his God; might as well go for broke. You turn on him with false fury, "Fool! You dare assume that Lord Elfanderel is so weak as to need an escort?! The endless hordes of magi from the Orient can not even match a tenth of my Master's power and grace! I should force you to prostate where you stand."
"Ah, forgive me for my transgressions; I simply could not grasp the might your Master wields, Saber." Heh, this was kinda fun. You turn to Shirou, "Is there anything else you require from the priest, Milord?"
"Umm...no, not right now; thank you Saber." Phew, glad he was smart enough to catch on; though it should've been fairly obvious given how you were acting. Now to fuck with the priest further...
"Kotomine; you fake smile cannot fool me, for the eyes are the gateway to the soul. I know what you truly are inside." Again, bullshit; but you should be able to get something outta him with this.
He becomes shocked the moment you say this, "I...I don't understand Saber, I am a simple man of the clo-"
"Do not lie; mortal! I can see the true darkness within you, what it hungers and desires. Yes...deep down, you feel it don't you? Lurking from within, defiling your faith and trampling on whatever goodness was instilled into you by the God you serve..." More BS, but it looks like you're hitting gold here.
"I...I have been forsaken by God; what other reason is there for a man such as I to exist? A man who's very being spits upon the Lord's gospel?!"
This was Grade-A stuff here, man. Time to continue, "Heh, is your faith so weak; Kotomine? Is it not clear what the Lord asks of you? Your 'curse' is a gift, bestowed by the very God you feel abandoned you..."
He looks distraught, every word you speak an arrow into his heart and soul; pleadingly he begs, "Why? What purpose does God have for a man who only finds joy and pleasure from the suffering and misery of others?! Why would God make one of his flock a warped, perverted monster?!"
Time to nail the final nail into this coffin of bullshit, "Why, to fight against the evils that go against him; of course. A normal man will break, being forced to fight against such monstrous beings who's very essence defiles the world. Who require such gruesome means to vanquish; means that would break lesser men. But you; you were made to bask in it, in the slaying of these monsters. To enjoy watching the enemies of the Lord squirm in agony as you used the very means they used to blaspheme against him as their punishment. Lesser men will break, Kirei; but you...you will grow, and flourish."
"God has chosen you to be the unbreakable bulwark against all that is evil; making you unable to be broken and warped by their whispers and temptations, for you are already one who basks in such. But it is not the suffering of man you bathe in; but of those of demons and heretics."
"Do you understand; Kotomine Kirei?"
"............................Yes." The man looks as if his entire worldview was torn to shreds; only for it to be a hollow imitation of what his life really was.
"I am sorry; Saber, Lord Lichtenstein, but I must pray and attend to my duties as a man of God. You may come at any time if you have further need of me. I must...pray..."
Mission Accomplished: Mindfuck of the Mullet Mastermind. You give yourself a mental pat on the back, nod at Shirou, and the both of you leave the Church. Shirou has this awestruck look on his face; like it was his birthday and Christmas combined. Not sure why he has that look; but whatever.
Then, you hear a little girl speak; "Hello, onii-chan~."
[X] See who it is
[X] Hah, fuck it; GTFO
[X] Scare them off with an epic speech and boast
[X] Write-in