Taking Shirou back to his house was quite simple, the problem was leaving said house. Normally it would have been a simple task, in fact it should have been a simple task, yet that damn protagonist aura that brings trouble to everyone around him-
"Master, we need to leave, fast" With a slightly somber expression on her face, Aqua addressed her master.
"Is it an enemy servant?" Slightly surprised by the expression on Aqua´s face, Rin started wondering what could make her react that way. Caster and Assassin won't leave Mount Enzou, Saber hasn't been summoned, there is no Archer in this war, Rider shouldn't be hard to deal with... that would leave only Lancer and Berserker, if it is Lancer then there is no much trouble, if it is Berserker on the other hand...
"Indeed, Berserker is coming, and he is coming fast."
Damn
"The worst case scenario huh? Get us out of here Aqua."
"I apologise master, but they already sensed us..."
"So it´s to late huh? How confident are you in beating Berserker?"
"If it was just him then it wouldn't be any trouble, my class is designed to deal with Berserker, the problem is his Noble Phantasm"
In an instant a huge muscular man appeared carrying a white-haired little girl on his shoulder. Putting her down, he closed the distance between him and Aqua.
Aqua, who felt a punch was coming in her direction chose to duck, before grabbing her master and jumping away. Her physical parameters were not the best and her mana wasn't in an optimal state due to having used her second Noble Phantasm minutes before, she may have absurd reserves of mana, but summoning a reality marble twice within less than 10 minutes is too much, even for her.
Seeing his first punch hit nothing but air, Berserker decided to swing his club instead. Due to the larger range of Berserker with the weapon, Aqua had no choice but to place her master right behind her and block the blow with her Divine Staff and, while she felt annoyed at having to use her first Noble Phantasm to physically block someone's attack, she didn't really have much of a choice.
Sensing the divinity within the staff, Berserker showed a confused expression. He may be consumed by madness, but as a demigod himself he knew the danger divinity poses. Quickly retreating towards his master, Berserker assumed a defensive stance.
His master, most likely understanding that there must be something about the staff that would cause Berserker to come by her side and protect her, chose to not send him to fight just yet and instead ask a question.
"What were you doing in Onii-chan´s house?"
"Tsch, we should have stayed at the house and brought him after eating dinner. Didn't you say trouble would come if we kept him? Trouble came as soon as we stopped keeping him!"
Rin was quite annoyed, Aqua already told her that Berserker was the most troublesome servant in this war so why did they have to encounter him?!
"Well yeah, but I didn't want to meet this scary loli so I figured dropping him off and leaving fast would be the best solution. Clearly I miscalculated."
"I AM NOT A LOLI!!" Annoyed by being both ignored and insulted, the white-haired girl chose to send Berserker to attack once again. While she knew the servant in front of her might be troublesome, Berserker was the strongest. "Berserker, finish them."
"Master, whatever you do, do not order me to finish them off. Leave, I will buy some time and then leave as well. If anything where to happen, the scabbard a placed inside you will heal you."
"What?! Don't be stupid, I will use a command seal to get us out of here!"
"Don't master, I already told you how important they are so it would be a waste to use one here, all I need to do is weaken him a bit and then find you."
"Humph! I refuse to leave you and run away! I am your master okey? That means I need to take responsibility in moments like this"
"Sigh, what a troublesome master I have" While she said that, a small smile appeared on her face. "Well then, if my master is so determined, how could I do anything to disappoint her!"
Blocking the incoming attack with her staff once again, Aqua started thinking of the different possible scenarios as well as their consequences. If she were to kill Illyasviel, Sakura would become the new lesser grail, which would make the task of saving her go from complicated to near-impossible.
Since her master doesn't want to leave first, the easiest solution would be to use a command seal, however they will be needing at least 5 of them later on, to deal with Zouken and Kotomine they will have to use at least one for each, later on to fight Gilgamesh and purify Angra Maiyuu she will need another two, one for each again.
Finally, she would need one more to fulfil her end of the bargain from the deal she is planning on proposing to Caster. Having only one remaining for emergencies she refuses to waste it here.
The best way to deal with the current situation is to either form a deal with Illyasviel or to weaken Berserker enough that she would have no choice but to retreat. What she has in mind for the deal would require using a command seal to actually accomplish, so it would leave them with no command seals in case of an emergency, however if they were to become allies with Berserker, they might not need to use a command seal to deal with Zouken and another one to deal with Kotomine.
In a way, it would be gambling to see if they can save two command seals for the price of one.
While all these thoughts were going on in her mind, her body started getting wounds that dripped golden-translucid water. She had successfully blocked or dodged most of Berserker hits, however even one landing was enough to hurt a lot.
"That's enough Aqua, I am using a command seal!" Her master screamed from afar, while the masters couldn't get close to the battle itself, it didn't mean they weren't able to see what was going on and, so far, Aqua was losing. "By the command seal, I orde-"
"Master don´t! Wether you use it to order me to defeat Berserker or to escape, our chances of saving your sister will lower regardless!"
Hearing Aqua´s words, Rin froze. She wanted to save her sister, she wanted nothing more than that. But would she be willing to let Aqua get hurt for it?
While Rin was going through a dilemma, the battle outside raged on, Aqua started enhancing herself, raising her parameter by one level, however it proved to be futile against someone who had all the physical parameters at least on A.
While she indeed could deal more damage as well as receive less damage, it wasn't enough to overcome the barrier the difference in parameters provided.
As she kept on taking hits, she chose to make a deal with Illyasviel, the problem would be wether she would accept or not. Right now the problem was how to make her stop Berserker and actually listen to her.
"Illyasviel! I can tell you what happened to your parents!"
Illyasviel, who so far had being watching from the sidelines while occasionally giving commands to Berserker, froze. It was clear by her expression that she was furious
Aqua however kept going.
"I know why Kiritsugu never returned! And why you are seeing your mother!"
By this point, Illyasviel was visibly shaking.
"Berserker... KILL HER!"
[ Aqua pov ]
Well... this didn't go as planned.