"Yeah, I know. It's that legendary cup, right? The one said to hold the blood of gods, capable of performing all kinds of miracles and even granting someone the world. But isn't that just a scam?"
Shinji nodded. "More or less. It isn't exactly like the legend, but the Underground Ley Lines beneath this city support a ritual capable of summoning something similar to the legendary Holy Grail. That is the Holy Grail System. They say whoever obtains the Holy Grail can have any wish granted. And the war you've been dragged into was established to complete the Holy Grail ritual and fight over the final Holy Grail—the Holy Grail War."
After that, Shinji gave Shirou a simple explanation of the Holy Grail War: what Servants and Masters were, what Heroic Spirits actually were, the relationship between the two sides, and how Command Spells could restrain Servants while also serving as a source of magical energy or powerful magecraft.
Shirou stroked his chin and nodded. "I see. So the Holy Grail selected seven magi in advance, and the proof is the Command Spells on my hand. The chosen magi then summon Heroic Spirits like Saber as their Servants. Once all seven Master-Servant pairs are ready, the Holy Grail War begins..."
"That's right."
"But, Shinji, there's still something I don't understand. If the Holy Grail is such a good thing, why do people have to kill each other over it? Why not just split it among everyone?"
"You should ask the overseer of the Holy Grail War that later. I need to go see him anyway. As someone who knows about the Holy Grail War, I accidentally became a witness and nearly got silenced. He's the only one who can help me with that."
"An overseer?"
"Yeah. He's someone who knows