Author: I finished E-4 earlier than expected. Since EO won't be releases until next week, Chapter 02 won't have a delay. In AL, since I'm done with Essex's air raid, I'm gathering gold blueprints for Sandy's retrofit for now.

This has yet to begin...

It's been six months ago since Tirpitz abandoned Iron Blood and disappear somewhere. Bismarck searched for her ever since she left, but she made no progress. She wasn't aware that Tirpitz had escaped to another world along with a "barely tolerable" companion. Since that was unknown to Bismarck, she continued to track her younger sister's whereabouts within the current world.

"Where could you be hiding...?"

Bismarck relaxes her back on her chair while she ponders inside her personal office. In her hand is the mysterious metallic Siren-made cube that Tirpitz gives as a sudden present before her inevitable betrayal.

"Why leave this thing to me? Is there something you wanted to tell me before you betrayed our nation?"

Tirpitz offered no explanation or clue when she gave the present to Bismarck on the day she decided to leave Iron Blood for good. This left Bismarck to speculate for months but couldn't come up with a reasonable explanation for the mysterious present. It didn't specify where Tirpitz was headed but it showed a conversation between her and King George V.

"I have been observing King George V but she isn't doing anything suspicious. What is her connection to Tirpitz? What does she know about her betrayal?"

When Bismarck saw the projection which recorded the two's conversation, Bismarck immediately suspected King George V of being an accomplice or at least aware that Tirpitz already planned her betrayal. She wanted to know about King George V but she found nothing suspicious on her even after months of secret observation.

"Tirpitz, why did you betray your own nation? Is it truly because you blame me for Tyrant's future?"

Bismarck fiddled with the small object still in her hand, sighed and asked herself about what happened six months ago. Tirpitz struck down Bismarck and before she left, she told Bismarck how she viewed Iron Blood as pointless nation and Bismarck as a pathetic leader. It sounded like it was Tirpitz's repressed thoughts but Bismarck felt like there was more truth to it.

"...?"

She returned the object back into the small box and hid it inside the right drawer on her desk when she heard knocking on her door. When the visitor entered, Bismarck straightened herself with her usual stern expression.

"Graf Zeppelin? What is it?"

"Someone from the Sakura wanted to see you. It's that old battleship Mikasa"

"Sakura's former fleet leader? What could she want?"

"I don't know but she said there's something important she wanted to tell you" Graf Zeppelin shrugs her shoulders

"It must be important since it's coming from one of the least person I expected. Bring her here"

"Understood"

Graf Zeppelin leaves as soon as Bismarck gives the command while Bismarck herself is curious to what the Sakura Empire's Mikasa wants from her.

"Hmm. What could Sakura's former fleet leader want from me?"

While waiting for Graf Zeppelin's to fetch Mikasa, Bismarck brings out the small Siren device out of the drawer.

"..."

Bismarck stares at the object for two minutes straight but the sound of knocking interrupts her. Graf Zeppelin brings Mikasa to the office and closes the door behind, leaving the two to speak in private.

"It's pleasure to meet you in person, Bismarck of Iron Blood" Mikasa greets her in a friendly manner

"It's an honor to for me to meet the legendary battleship of the Sakura Empire"

Bismarck stands and greets the veteran battleship in her own way as well. Even if Mikasa gives off a gentle and friendly atmosphere, Bismarck is naturally stern and serious around everyone since she tends to act like a disciplined leader.

"Is there something you need? This visit is one the least I expected"

"Yes. It's related to you so I had to meet you as soon as possible" Mikasa's expression turns serious

"From your expression, it's clearly important. What is this about?"

"I heard about what happened six months ago. The one that involved your sister and someone called Tyrant"

"...?!"

Even if it's been six months since that incident, the events is still fresh on Bismarck's memory, especially the moment when Tirpitz decides to abandon Iron Blood and disappear ever since.

"About...my sister. What is it about Tirpitz?" Bismarck hesitates for a moment

"I've been looking into a mysterious Siren called [Aurelius]. While I was tracking her existence and possible location, I came across an odd Siren"

"An odd Siren?"

"I fought a Siren who displayed human-like behavior. When I fought her, she mentioned several things. One of those things is regarding the incident with Iron Blood six months ago. What happened in this incident"

"What happened, you ask? My own sister betrayed me. She struck me down and declared she no longer fights for Iron Blood. She...was already planning even before the last battle with Tyrant"

"..."

Mikasa can see how Bismarck still couldn't understand and accept why Tirpitz decides to betray Iron Blood before the last fight with Tyrant. She didn't comment or express her pity as she believes Bismarck is someone who dislikes the pity of others.

"I see. That explains why she was with the Sirens"

"The Sirens?"

"I'm investigating about the existence of Aurelius. There were others in the residual memory but your sister was there"

Mikasa brings out a core of data bank of some sort which she wraps around a cloth. It's an interesting object she obtains while tracking down the elusive and mysterious Siren who has been present even before the war.

"It's from a purple Siren Explorer I beat up while I was in the Northern Union territory"

"What is that?"

"This thing is like a recorder which projects what it was and heard before I sunk it. I found it while I had Akashi examine this thing"

Mikasa flips the Siren core that has slight damage after the brief fight with her. Mikasa twists the object by holding it with both of her hands and activates in the process. The small processor inside it faintly hums and the lines around the object glows.

"Watch"

The scenery of a formal office disappears and they find themselves standing in an unknown location with steel walls and several machine parts lying around. It projects the location base on what the Siren records on its surroundings during that time.

"A Siren?" Bismarck frowns

A Siren with curly tips and reading what looks like newspaper, gently hums while swaying her feet. About ten seconds later, Tirpitz walks in and approaches the unknown Elite Siren.

"That's Tirpitz?!"

"Correct. That's why I wanted to show this to you" Mikasa nods

"What is doing with the Sirens?"

"Just watch"

Mikasa places her index finger between her lip, gesturing Bismarck to lower her voice and tells her to just observe first.

"You and that heavy cruiser is surely enjoying your stay in that other world"

The Siren closes the newspaper, folds it,and puts it on the side. She looks upset at Tirpitz but the latter clearly doesn't care about what the Siren thinks of her.

"I may not be doing anything now but I'm still doing my task. That's why I'm staying around the Bermuda while that girl dealing with any possible threats elsewhere" Tirpitz smiles

"You really are taking your time"

"I have spare time. I even accessed the archives and found about Code: Null - Project Ghost, an unknown shipgirl from a parallel world. There was no match of Ghost's counterpart here"

"Project: Ghost was a new existence and it was so much of a dangerous existence that it annihilated both shipgirls and Sirens in a parallel world. You know about it, right?"

"I'm aware the Observer and the other tried to bring her here in this world. That's the thing that caused [Redaction] two months ago. It's terrifying how such thing came to existence"

"Fortunately, Project: Ghost was already an unstable existence that upon forcing it out of its world, it deconstructed most of its existence. Ghost lost what's left of its mind and was reduced to its Mental Cube when Aurelius detected it"

The Elite Siren then projects a silhouette with owing red eyes right before Tirpitz. It's an unknown shipgirl who isn't in the normal classification but it somewhat resembles a normal shipgirl, only that it has no proper appearance other than its shadow.

"Code: Null but commonly known as Ghost. I wonder...who it was before becoming nothing but the strongest defective weapon"

"Ghost wasn't based on any shipgirl. It was an entirely new existence without any history. As a result, it didn't fully develop any personality" The Siren answers

"..."

"You shouldn't be concerned about Ghost.. That mindless weapon is still sealed and guarded by Lancer"

"Just by herself? What if a ruckus occurs and it causes a breach?" Tirpitz expresses her concern

"Aurelius has other priorities. We need to deal with certain girls who shouldn't meddle in our affairs"

When the Siren mentions certain threats, Tirpitz frowns and goes silent for a minute or two. She's aware of who the Elite Siren is referring and this made uneasiness visible in her expression. She has her mission and she will obey them, even if she has to confront the people she knows.

"It doesn't really matter who they are. I will obey Aurelius orders since it's my choice to work with a bunch of weirdos"

"Who are you calling weirdos?!"

"..."

The calm-looking Siren raised her voice and puffs her cheeks when Tirpitz insults her. The latter faintly chuckles upon seeing an intimidating Siren having mood swings, a human trait visible to the other group of Sirens.

"Anyhow, I have to go to the Mariana Trench. Dredger keeps asking for help since she shaving trouble with the shipgirls there. Honestly, she could talk care of it herself but she's being such a wimp" Tirpitz clearly finds it annoying

"How about your friend?"

"She's with Linker somewhere in Denmark. As long as she doesn't cause trouble, I'll let her be"

"Just keep an eye on your carefree friend who loves to insult others and doesn't bother to be careful"

Tirpitz stops in her tracks and briefly turn towards the Siren, briefly smirking before taking her leave. She then leaves the area with the Siren silently letting her leave while crossing her arms. After the memory finishes replaying, the scenery around them returned to normal.

"Tirpitz...is with the Sirens..."

From the memory alone, it is clear to Bismarck that Tirpitz is clearly siding with the Sirens when they're suppose to be the enemy.

"Your sister did really betray you, Bismarck. This is what I wanted to show you" Mikasa wraps the object again

Bismarck lowers her head and clenches her fist, not seeing a reasonable explanation to why Tirpitz is working with the Sirens after the events six months ago.

"In that memory, Tirpitz said she's working for Aurelius. I want to know more about this Siren"

"If you want to know more, there's only one way to find out about it"

"Please tell me. I want to find out why would Tirpitz work for the enemy"

"Then you're going to be in for a long trip..."

It doesn't matter where she has to search, Bismarck displays she's determined to seek answers behind the meaning of Tirpitz leaving Iron Blood and allying herself with the Sirens. This might be her only opportunity to find Tirpitz and Bismarck isn't going to let it slip after six months of searching.