Quick notes about this:
1. If you have not read the ending to Walk in the Shadows, do so right now. It explains a few details (granted, it isn't very good, and if you don't wish to read it, basically Prussia's in Ikebukuro, leaves, and leaves something behind that points Izaya towards the mansion in HetaOni.)
2. Some scenes have been changed up a little.
3. The pairings that will be suggested here are ShinraXCelty, MikadoXAnri and hinted Shizaya on Shizuo's part.
4. I refuse to say who will be the HRE for Izaya, but the most I can say is that it will not be a kid doing the role.
5. The confirmed roles for the characters (besides the obvious Izaya being Italy) are:
Firo, Ennis, Maiza, Czeslaw, Saburo, Erika and Walker: Crew outside the mansion.
Isaac and Miria: Extra characters.
6. This and Walk in the Shadows would take place after HetaOni with a ending different than what I think the creator of said series actually has in mind, and the nations will go to help the crew in the mansion...with a bulldozer.
7. There will be side chapters that show what's going on elsewhere during the main chapters, such as the remaining nations watching the micronations.
I own nothing.
This is a fan interpretation of "What would happen if characters from Durarara! were in the HetaOni/Ao Oni mansion".
As with HetaOni, the main objective is to survive and escape, but it bears little similarities with Ao Oni after that.
I apologize if this seems like a copycat product or is ripping off anything whatsoever. No benefit is being made out of this, and is not meant to show disrespect to the creators of HetaOni or Ao Oni or anyone involved with either games production.
There will be surprises as you continue on. For example, references to other popular culture, including Durarara!'s sister series Baccano! and twists you may have expected if you watch HetaOni.
There will be references to a fanfic crossover called "Walk in the Shadows", as it explains how and why this story started as such. Its last chapter is the only one necessary, however.
Hetalia belongs to Himaruya Hidakez
Durarara! and Baccano! belong to Ryohgo Narita.
All other series mentioned and/or referenced belong to their respectful owners.
Do you still wish to go on?
Somewhere, in a forest not that far from Ikebukuro, a mansion loomed in the center of it, almost giving off the appearance of a castle.
Izaya, Shizuo, Kasuka, Shinra and Celty stood at the entrance to this mansion. Celty, being…well, Celty, did not appear to like the mansion.
"Hey, flea, is this where that booklet said the mansion would be?" Shizuo questioned Izaya.
"Yup. I'm surprised to find such a building in the middle of the forest," Izaya admitted.
[Guys, I don't think it's a good idea to enter this mansion. It seems so creepy!]" Celty complained.
"Don't worry, Celty, if things get bad, I'll protect you," Shinra promised.
"[But that booklet said we might get attacked by things that look like aliens! I don't want to go in there!]" Celty typed out.
"Celty, it will be fine, I promise," Izaya promised, the group entering the mansion.
Inside, it seemed to be clean. No dust, no creaking floors, not even signs that anyone had lived there…yet. Long halls led deeper into the mansion, and stairs led to another floor.
"This place does not feel safe…" Shinra noted.
"It's about as clean as clean gets with creepy mansions," Izaya commented.
"[You guys can explore the mansion, but I'm getting out of here. I do not feel safe,]" Celty declared, walking up to the door.
To her surprise, it refused to be opened. The Dullahan desperately tried to open it, but to no avail.
"Uh oh…" Izaya muttered.
"[Shizuo, can you please punch this door open?]" Celty asked.
Shizuo strolled up to the door and punched it as hard as he could. To his shock, it didn't open.
"What the…why won't it open?" Shizuo demanded to know.
"I wouldn't know," Izaya admitted.
Shizuo ran up to him and grabbed him by his jacket.
"Listen, flea, if this is your idea of a joke, oh so help me…" the blonde man hissed.
"Do you think I'd go as low as to lock the door to a strange old mansion where, perhaps, Iwould want to leave from?" Izaya questioned.
"Okay, before Shizuo and Izaya tear this mansion down…wait, go and do that," Shinra joked.
"[Shinra!]" Celty berated.
"I was kidding! Anyways, we're better off finding a way out of here before something bad happens," Shinra reminded.
Shizuo let Izaya go.
"Fine…but if he pulls something…" the former bartender threatened.
"I won't. Geez, Shizu-cha-"
"[I'm just going to stop you right there, Izaya,]" Celty stopped.
Suddenly, the sound of a dish breaking got Izaya's attention.
"Someone else is in the house?" Shinra guessed.
"Not that I know. I don't think I told anyone else," Izaya recalled.
"Well, that's unsettling," Shizuo muttered.
"I'll go check it out. I'll be right back," Izaya promised, heading towards the source of the noise.
A long hall stretched to the kitchen, where Izaya felt a draft.
"Geez, this is cold. The mansion isn't as well-kept as I thought," he muttered.
He glanced around quickly and found a plate broken near a table. Dark stains covered it.
Wait. Were those stains there before?
Izaya held a hand up to his head and headed over to a wall to rest his head.
"Okay, this is not funny if someone's trying to pull a joke on me," he muttered.
Picking up a shard of the plate, he hurried back to where the others were, only to discover they were gone.
"…not funny, guys!" Izaya shouted, annoyed. His face soon took on a slightly downcast look before he headed past the stairs to somewhere else.
Celty did not trust Izaya enough to think he wasn't planning on anything shady in this mansion. In fact, she was grateful Shizuo declared they leave Izaya for dead and split up.
"The flea obviously has some sort of plan up his sleeve, and I don't want to put up with him in this mansion," the ex-bartender declared as they had split up.
Maybe it wasn't a good idea to trust Shizuo. He hates Izaya, sure, but Izaya looked like he knew the place by heart.
Suddenly, Celty stopped dead in her tracks. Something huge, pale gray, and not even remotely human was entering a door. If she could have, Celty would have screamed, but where would that have left her?
One upside to not having a head? the Dullahan thought, nervously.
She hurried into another room, discovering it was a bathroom. Nothing was off about it, besides the fact it had no windows.
Returning to where she had initially arrived with the others, she headed up the stairs and into a room. Something was off in the room…
Maybe it was the fact that the curtain was shaking.
Celty moved the curtain to discover a shocked Shizuo, who was gripping the curtain tightly.
[Shizuo, what's wrong?] the Dullahan typed out.
No response came, just Shizou staring at something she couldn't see.
Refusing to let there be no sound in the house, Celty slapped Shizuo.
[Shizuo Heiwajima, snap out of it! What happened?]
Shizuo blinked, then greeted, "Oh. Hey."
[Shizuo, what happened?] Celty repeated, not as urgent this time.
"Well, I don't remember much, just Shinra and Kasuka running past me and a whole bunch of…I dunno, things," Shizuo explained.
[Well, that helps…do you know where they went?] Celty questioned.
Shizuo shook his head, then handed Celty a key.
"I don't know why I have this, but I think it'll lead somewhere," he admitted.
[…thanks? Can you come with me?]
A brief silence followed before Shizuo shook his head.
"I have no sense of direction, so I'm just going to stay here until Kasuka or Shinra finds me," he informed.
[Well, good luck.] Celty left the room, key in hand.