Shikai:(Scared whisper) What did I just do…

The nun smirks upon hearing those words from the boy.

Kiara: You must be my master, correct?

Shikai: (Shouting) YES! I AM!

Shikai: (Thinking) AHHHHHHH! WHAT WAS IN THAT BOOK!?

Kuro faints again. And Shikai chidori's him back to life.

Shikai: We both know about you Kiara. You may have redeemed yourself during Ooku, but we already know the rules of our contract. If we fall for your charms and advances you become a Beast, and if we remain pure, you'll completely reform.

Kiara: Ara Ara~ a smart one too! Let's see how long you can go before you break Master! Fufufufu…

Shikai: (Annoyed) Just get inside.

The nun walks inside and waits on the couch.

Kuro: WHAT THE HECK MAN!? WHY DID THAT BOOK SUMMON HER!?

Shikai picks up the book and sees its cover. And with it his eyes widened in terror.

Shikai: (Horrified) It's the oldest copy of The Little Mermaid known to mankind. The cover is signed by Hans himself! GOSH DARN IT HANS!

Kuro: (Trying to see the bright side) We can fix this, we can fix this, we can fix this. You still got the scale and the Sake. Try the scale next.

Shikai quickly removes the book and burns it with his fire magic. He then puts the scale in the middle of the circle and tries again. He channels his magic and the pure magical might required almost makes him faint. The second resulting pillar of light is bigger than the first.

?: I have come in answer to your summons. I bring the judgment of the scales and the justice of the stars. My name is Astraea, a terminal of all good in this entire realm. Even as my Master, are you prepared to be measured?

Lady Justice makes her grand entrance. Shikai and Kuro both are in awe for different reasons.

Shikai: (Thinking) YES! YES! YES! ONE THOUSAND TIMES YES! THE HERALD OF JUSTICE IS HERE! THIS IS WHY I HAD THE SCALE! IT IS MY DESTINY TO BECOME A HERO!

Kuro: (Thinking) You lucky bastard!

Shikai: Welcome to the team Astraea. I'm prepared to be judged even by you. I'll do whatever it takes to become a hero.

Astraea: I see, a noble goal. I'll help you see it through in the name of justice.

Shikai: You can take a seat on the couch inside if you like. Just ignore your other teammate. Summoning her was a freak accident. And unfortunately, I'm stuck with her.

Astraea walks inside and takes a seat on the couch. The nun tries to start up a conversation.

Kiara: So you must be the first of my two new teammates. What do you think of Master?

Astraea: I can tell by his aura alone that he has had a depressing past. His wish of becoming a hero is to make sure nobody experiences what he went through. And I can see that the scales are not in your favor. Try anything funny with Master and I'll make you wish you were never summoned.

Kiara: (Thinking) You know what they say, the ripest ones are the sweetest! But with Ms. Justice around it's gonna be difficult. Guess I've gotta play the waiting game.

Kuro: Dude. It's like you're playing FGO. Also, when did you get that scale?

Shikai: I got it from a trip to Greece 4 years ago. Now, time to put this bottle of Sake to the test.

Shikai uses his magic to teleport his scale back to his room and puts a bowl in the center of the summoning circle he pours the sake in the bowl and channels his magic for the third and final time that night.

?:Assassin, Shuten-Douji. Fufu. Please accept my gratitude for summoning me. I will do as I please but... you don't mind, do you?

Shikai: Not at all. Just wait in the living room with the others and I'll get you three acquainted in a bit.

Shuten joins the two on the couch while Shikai and Kuro discuss the former's servants.

Kuro: I know you were trying to summon Shuten and Astraea, but who did you want as your third?

Shikai: I was looking for my fluffy replica of Morgan's Throne. But I guess I gotta make due. But quick question, are your parents ok with you spending the summer at my place?

Kuro: Yeah. They're working on a huge business project and they have to do a business trip. SO they gave me the OK.

Shikai: I'm gonna get everyone acquainted while you summon your servants.

While Shikai goes inside, Kuro traces a katana and puts it at the center of his summoning circle.

Meanwhile…

Four recognizable figures get off a plane.

Rin: You sure it's a good idea to form an alliance with them?

Artoria: I can say the same about Archer.

EMIYA: You try to kill your past self ONE TIME!

Shirou: It's our best shot. And one of them aspires to be a hero right? We'll show him the way.

Also meanwhile,

Bunkyo Ward, Tokyo

A kid is shown in a cryogenic chamber. A little girl approaches the controls and puts in the disable command.

Da Vinci Lily: Master, it seems that another contestant has entered. Check your Cyber Band.

The kid steps out of the chamber as the entire room starts to freeze just by his presence alone. His shaggy white hair and white outfit gives off serious accelerator vibes. He checks his band,

?: IsekaiProtagWanabe24 huh?

Frost: (Sinisterly) Da Vinci, let's go on a Beautiful Journey.

Pairs introduced and Buddy NPs

Shirou Emiya and Artoria: Legendary Duo Excalibur Blade Works

Rin Tohsaka and EMIYA: Superior Blade Works

Frost and Da Vinci Lily: Ice and Fire Beautiful Journey

Also, try to catch the Jojo Reference for bonus points!