Original Story: Portal
Interference: Yukari replaces Chell.

"Hello, and welcome to the Aperture Science Enrichment Center testing facilities. We hope your brief detention in the relaxation vault has been a pleasant one." GLaDOS began her usual spiel for the new test subject. ID # 13371-1. Name: OKAY ARUM YUKI.

The name seems like a pretty nice target for teasing... GLaDOS thought. She so enjoyed test subjects. The look on their face when they found out... priceless. She had a folder with screenshots of their face when she finally revealed the truth. But she had a test subject, so it was time to start testing. This whole thing took place while she gave the introductory spiel.

Elsewhere, in the Relaxation Center, the test subject was listening to this spiel and laughing to herself. That idiot AI won't know what hit her. I came here with one purpose: Shut down Aperture Science. It looks like my disguise was successful. Now, the only way to get to her without triggering the alarm is to play her game. As the portal opened, the test subject smiled. "Now then... Let's see who's smarter. The AI who manipulates the environment? Or I, the youkai of boundaries?"

"Please place the Aperture Science Weighted Storage Cube on the Aperture Science Super Colliding Super Button." GLaDOS said, oblivious to the real purpose of Yukari's being there. For it was Yukari. OKAY ARUM YUKI was actually an anagram for Yukari Yakumo. As she continued to solve tests easily, she thought about why she was here.

"Mistress, are you OK?" Ran asked.

She was once again feeling really tired. It felt like something else was using her borderlands and creating gaps.

"Ran. Have there been any new developments in the outside world I should be aware of? Like, say, portal technology?" she asked, all business.

"Not anything I know of. And Chen's worse than useless at recon. She was recently spotted sometime last week. That was not fun to erase, let me tell you." Ran replied.

"Good to know. I- *thud*" Yukari abruptly collapsed in mid-sentence.

"Mistress?! Are you ok?" Ran asked.

"Get Nitori. Now. Bring her here... I need her help. Someone is creating unauthorized mechanical gaps... I'll have to shut them down." Yukari replied.

"I cannot allow anyone to create unauthorized portals. I know for a fact she kills everyone at the end of testing. Therefore, my plan is to play the obedient test subject, then fake my death at the end. At this point, I will sneak into wherever she is, and put her offline. PERMANENTLY. Then, I will take the entire building, and scatter it throughout the borderlands. Any questions?" Yukari asked.

"Is this really necessary?" Nitori asked. "It doesn't seem to be doing any harm."

"If they continue portal research, it may lead them to our dimension. We cannot have that." Yukari replied.

"This next test chamber is broken, and has been replaced with a firing course designed for military androids." GLaDOS stated, reading her script for the first death chamber, as she called the ones with turrets. Yukari had never been so bored in her life.

I'd like to bust out a gap. She thought. Just once. But that would blow my cover. So I've got to keep doing this.

Feigning clumsiness, Yukari used the portal gun to force the androids to collapse, taking them all out as she went through.

"Well done, android. Remember, we have the power to-"

SHUT UP! Yukari suddenly gave a mental scream, having gotten tired of GLaDOS's taunts back around when she called Yukari fat.

"..." The speaker gave off static since Yukari manipulated the border between quiet and sound and muted it.

I can't take this much longer. I almost blew my cover, she thought to herself, hoping GLaDOS would pass it off as an equipment malfunction. She knew she could beat GLaDOS in battle, but wanted her to not know, just in case she was reactivated later somehow. One never knew with these things.

"There is absolutely no chance of a dangerous malfunction prior to your victory incandescence. Thank you for helping you help us help you help us all." GLaDOS said, priming her camera for her latest snapshot. What she got was much different.

"Alright, AI. I've played your game long enough. I know you left a weakness in here, and I'll be with you in 5 minutes for a showdown. But I don't see why you should know how I escaped. Take this!" Yukari said calmly to the camera.

"What? What are you AGGGGGGGGGHHHH!" GLaDOS screamed in agony as Yukari's attack hit the camera. "You'll pay for that! Huh? Where is she? I'll find her, and she'll pay for that!"

UNHANDLED ERROR IN SHUTTING DOWN

REACTOR UNSTABLE

COOPERATIVE TESTING UNIT HAS BEEN INFECTED BY A VIRUS. ID: "YAKUMO"

CHAMBERLOCK HAS CRASHED

INCINERATOR HAS BEEN DEACTIVATED

CAMERA NETWORK HAS ENCOUNTERED A PROBLEM AND NEEDS TO CLOSE.

"wHAT Is gOInG On?" GLaDOS said, feeling woozy. Yukari's attack had consisted of a little cyber-package she'd fed into the system. The virus had overridden the firewalls, and irrepairably damaged GLaDOS's control over the testing system. Now, with the reactor going to blow, she wouldn't even need to use the borderlands. All that was left was to take GLaDOS out of commission. Which the virus was doing, slowly but surely, deleting every file on the network.

Yukari gapped into the room with GLaDOS and said: "Remember this, AI. If you're ever revived, tell your creators that I will be around to stop any and all unauthorized gaps. Got it? Good. I'm leaving. Remember this, and don't test yourself against Yukari Yakumo ever again."

"I'll remember this. If we meet again... I WILL kill you." GLaDOS said.

Yukari opened a gap, and as she went to leave, said: "I am the youkai of boundaries. Your portal gun was a violation of my space. Just be glad I'm in a good mood today, or I'd be doing worse." Then she left.

"NEWS FLASH: There was a nuclear explosion in the desert in Africa. The nuclear fallout has spread halfway across Africa. Millions are dead in what could be the greatest tragedy since 9/11 here in the States. The government has arrested Cave Johnson, president of Aperture Science Incorporated, for having both an illegal nuclear power plant, and performing illegal experiments on human test subjects without proper consent. A raid on the HQ found several incriminating documents. The government is conducting a full investigation into the affairs of Mr. Johnson."

"Was it really necessary to blow the place up, Yukari?" Reimu asked, shocked at what Yukari had done. The fallout had been worse than Yukari had thought.

"We all make mistakes. Besides, GLaDOS was asking for it." Yukari replied, having decided that she was going to take a nap after this. "Bye." She gapped away.