The operating mechanism of the Greater Grail when it is not activated is very simple. It draws a limited and controlled amount of magical energy from the ley lines, storing energy until it reaches the threshold required to activate the ritual known as the Holy Grail War.
To put it simply, the Greater Grail is just charging up, and once fully charged, it activates. Originally, the Greater Grail was still a bit short of being fully charged, but Heartless' actions filled up the remaining gap, causing the system to activate.
If that were all, it wouldn't be a big deal, but the amount of magical energy that surged in exceeded what was needed, inevitably impacting the Greater Grail. This is also why Justeaze was so eager to contact Shinji.
After waiting ten years and nearing success, having something go wrong at the last moment would shake anyone's composure.
Justeaze was already anxious, so it was no surprise that Shinji's face darkened the moment he stomped heavily on the ground.
"Even in death, you cause trouble! You won't let anyone have peace! I should have destroyed your body and soul without hesitation."
Shinji wasn't careless, nor was he overconfident. Capturing Heartless alive instead of killing him was part of the original plan to probe Hishiri Adashino.
Heartless and Kariya Ririko were both protégés of Norwich, the founder of modern magecraft and its biggest benefactor. This family is famous in the magecraft world as the "Daddy-Long-Legs family of the Clock Tower," who support talented young people for years without asking for anything in return, nor imposing any restrictions on those they support.
Though many families criticized this tolerant, almost indulgent attitude as foolish, it also won the hearts of many young people. Countless talented individuals joined the Norwich family, with some even changing their surnames and becoming adopted members of the family. Heartless and Adashino are such individuals, and they are as close as siblings.
Although it's unknown why they later left Norwich and went their separate ways, at least Adashino still harbors some feelings for Heartless. Adashino boarded the train after receiving news in advance, coming to find Heartless. She made several moves in this regard, such as stepping in to resolve the Trisha case while Waver was recuperating, and later assisting Waver in setting up the binding ritual for Heartless.
On the surface, it seems like she did this to bring her estranged brother back to the Clock Tower, but no one knows her true intentions. This is why Shinji planned to use Heartless to test Adashino's true feelings.
However, now not only has the plan failed, but Adashino might even hold a grudge because of it. Most importantly, this could affect Shinji's ten-year plan, so, understandably, he would react this way.
One stomp wasn't enough to relieve his anger, so he continued stomping several more times. Human strength pushed to its limits and caused booming sounds in the sand, kicking up a cloud of dust.
"Shinji, are you okay?"
On the other end of the phone, Justeaze heard the cursing and the noise, and asked with concern, her clear voice like a cool spring calming Shinji's anger considerably.
"I'm fine."
"That's good. This is just an accident, not a real failure, so there's no need to overthink it. Even if this fails, there will be next time, and the time after that."
"You're right. It's too early to call this a failure. The ritual starting ahead of schedule affects me and the other participants equally. Alright, I'll head back right away. Follow the plan on your end, focusing on securing our base and gathering intelligence. Don't rush into action."
"I understand."
"Also, try to get in touch with the old man and see how he reacts."
The old man Shinji mentioned is, of course, the Second Magician, Kischur Zelretch Schweinorg.
"Got it."
"Be careful."
"You too."
The call ended quickly. Shinji turned to Waver and asked, "You heard everything. I'm heading back now. What about you?"
Waver smiled bitterly.
"Even if I wanted to leave, I can't right away. There's still so much to arrange. And Faker needs time to recover."
"I don't need your concern," the female warrior snorted, refusing the sentiment.
"I've said everything I need to say many times, so I won't repeat myself. Do as you see fit. Arcueid, let's go."
Arcueid made a couple of "oh oh" sounds, then pointed to the nearby, battered Mystic Eyes Collection Train.
"What about that? Are we leaving it behind?"
"Uh, I almost forgot," Shinji slapped his forehead. Things that come too easily are often taken for granted.
"Could I ask Miss Rozay-en and the others to look after it for a while? I promise to visit and thank you properly once this is all over."
"I don't mind," answered the familiar imbued with Rozay-en's will, "but I can't guarantee its safety. The ley lines around here are already exhausted, so the train has no power and can't move. This is also the heart of the magus' territory. It won't be long before waves of magus start arriving— in this regard, they are more vampire-like than us vampires."
"Clock Tower—"
Hearing Rozay-en's blatant sarcasm, Lorelei raised an eyebrow and was about to speak.
Shinji quickly caught on to her thoughts and sent a silent message.
"Calm down, she's stating facts. Even if you can control the Barthomeloi, Trambelio won't listen to you."
"They will listen if you reveal your identity, and I vouch for you. Trambelio's people won't dare act rashly."
"So this was your real plan."
Shinji rolled his eyes. "My lady, the fire on my end is already burning hot enough. Can we not add fuel to it?"
Lorelei's mouth twitched slightly, using the wind to send her voice to Shinji's ear.
"This isn't adding fuel to the fire; it's the best solution. Do you have a better idea?"
"I do."
Shinji ended the telepathic conversation and spoke aloud.
"Arcueid, stay here and help me move the train to a safe place— you can provide magical energy for me, so you should be able to do the same for the train, right?"
"I can, but I don't want to be separated from you. It took so much effort to suppress my impulse, and there are still many interesting things to do together," Arcueid pouted, like a child throwing a tantrum.
"Come on, help me out. This train is the foundation of our future travels around the world. If we lose it, we'll have to go back to switching between different modes of transportation like before. Don't you hate that hassle the most?"
Shinji tapped her smooth forehead. After spending five years with her, he had already maxed out his soothing skills.