Author's Notes: I do not own anything related to the Marvel Cinematic Universe or with Yu-Gi-Oh!. All characters and respective media are owned by Marvel Comics, which in turn is owned by Disney, as well as Shōnen Jump and Konami respectively. Story takes place a few years before Iron Man and a few weeks after the events as seen in Yu-Gi-Oh! : The Dark Side of Dimensions. Enjoy.

Natasha Romanoff, also known as the Black Widow, is currently operating on a espionage mission to infiltrate the Kaiba Corporation in the darkness of night and acquire information that will interest her employer, Director Fury of the Strategic Homeland Intervention, Enforcement and Logistics Division.

The former KGB operative never would have guessed that she would have to extract information from a company that dealt with a child's card game but in recent years, the company's head Seto Kaiba certainly got their attention.

It appears that wherever Kaiba went, there were reports in various parts of the world of sites dealing with "darkening skies," "shadow games," and "mythical creatures." The red head tempted to roll her eyes at such fantastical claims as she moved quickly through the air ducts of the corporation, following schematics that she acquired from a computer in the building earlier. Instead, Natasha was more interested in realistic accounts, such as Kaiba self-destructing his own island after one of his tournaments and the recent space station he constructed. In addition, his recent duel with Yugi Moto led to a resurgence of the fantastical claims she's heard before, with "darkening skies" that appeared in Domino City. For a multi-billionaire who claims to focus on the game Duel Monsters, the construction of his own personal space station and constant repeated claims of potentially "supernatural" forces at play was the final piece of evidence that the billionaire is more than he claims.

Under the alias Natalie Rushman, Natasha arrived at the Kaiba Corporation in Domino City with a résumé to spy as one of Kaiba's new secretaries. Fury paid no exceptions to make the documents as authentic as possible and Natasha had no problem speaking and reading in fluent Japanese. Although she had infiltrated the Kaiba Corporation for a little over three weeks, the spy rarely saw Seto. Instead, she interacted with his younger brother Mokuba, who occasionally mentions that Seto, as head of his company, is currently traveling the globe to promote his new dueling technology for the card game. With that said, Natasha knew enough about the computers to locate her secondary target. If she couldn't interact with Seto and lower his guard, she will have to settle for the next best thing; his personal computer.

Snapping her thoughts back to the mission at hand, Natasha looked at the blueprints and determined she was directly above Seto's office. Folding the schematics into a small square, Natasha placed the paper into her form fitting stealth suit. Quietly, she opened the gated hatch and placed it to the side in the vent and nimbly landed on the floor. As she was doing this, her thoughts resurfaced. This feels too easy… A warning began to whisper into her mind when she felt her boots step on the fabric of the carpet…

…only to freeze when she hears a pistol already loaded and presumably, aimed right at her. The spy sighed and mentally criticized herself for not trusting her instincts. At least Clint wasn't here, she would never hear the end of it from him.

"Nice outfit. Must be a pain to squeeze into." The backhanded compliment was said in a sarcastic and smug tone. But what surprised Natasha the most was she expected to hear it in Japanese, not in English. "Turn around… slowly, with your hands above your head." The voice demanded offering no objections. As ordered, Natasha raised her hands in the universal sign of surrender and turned to see Seto Kaiba pointing a handheld pistol directly at her stomach.

Though the room was dark, Natasha could see his long white, sleeveless overcoat gleaming in the moonlight alongside his belt with large K and C initials though his black clothing underneath was less visible. His blue almost grey eyes were visible as well, trained on her like a hunter ready to release a trap for unsuspecting prey. The pistol itself is a M9, with a customized art piece on the grip. Though his left hand covered most of it, Natasha could barely make out part of wings and a head of a dragon of some kind. With that said, Natasha wasn't paying attention to the design. Instead, she was staring at the barrel of the pistol aimed no more than ten feet away from her.

Looking quite satisfied, the head of Kaiba Corp grinned. "Now that I have your attention, I expect your full cooperation. Make any movement that I have not requested, my finger might slip. And trust me, being a professional card player makes me quick on the draw." Kaiba warned, though his eyes gleamed dangerously as if daring Natasha to try something.

The redhead's mouth tensed into a firm line. Normally, she would have no problem disarming a lone attacker but Kaiba was far enough to not be disarmed and she was too close to avoid the first shot with the added disadvantage of her hands being raised. For now at least, she has to play by his rules but maybe distractions might work…

"I thought you were promoting your new technology in Paris by now?" Natasha asked, using the question as a means to determine Seto's awareness and to lower his guard.

Seto's eyes never left her face, his grip on the pistol still firm. "I left France early. Besides, that's not the point is it Natalie?" Kaiba remarked, the mention of her alias snapping the former KGB agent to attention as his grin deepened in smug superiority. "Or shall I call you Natasha Romanoff?"

At the sound her name, the former KGB agent's thoughts were racing. He knows who she is? What else does he know? Questions began to flood her mind over the possible damage Seto Kaiba might do to her and the agency as the trained assassin retained her composed demeanor. "Have you always known I was sent to spy on you?" The redhead asked, not bothering to be subtle considering her cover was blown for a while it seems.

Kaiba released a short chuckle, clearly amused as the situation became increasingly clear that he was enjoying every second. "Not at first." Seto admitted. "Whenever I'm away, Mokuba always updates me on new employees. Your papers looked authentic enough, but considering how much influence and power I have, it didn't take too long to realize you're not who you say you are." The billionaire responded before his amused grin turned into a frown. "Now, what do you people want with my company? And answer honestly, otherwise… my patience will wear thin." Kaiba ordered, placing emphasis on the word 'patience.'

The Black Widow paused for a moment, considering her options about how much information she will be forced to share. "The construction of your space station and claims of darkness are resurfacing in Domino City after your recent game with Yugi Moto has made you a person of interest to my organization. I was sent to investigate you on their behalf." Natasha said, merely stating her objective but withholding anything else involving with Fury and the spy network as a whole.

The redhead's emerald eyes analyzed Kaiba's face, with the spy noticing his demeanor changed slightly. More noticeably, she began to realize that Seto slightly lowered his aimed pistol from her person, though only slightly. "Tell me Miss Romanoff, do you believe in alternate dimensions?"

The question almost threw the always composed Black Widow off completely, with the redhead unsure how this conversation will go. "What does that have to do with anything?" Natasha asked, lowering her arms now that Kaiba's guard is lowering as well.

Kaiba's glare never wavered. "It's the answer your organization is looking for. Before I dueled Yugi, he played a game against a duelist named Diva who had the power to send anyone to an alternate dimension via a device called the Quantum Cube."

From anyone else saying that statement, Natasha would have easily call their bluff at such a ridiculous and outlandish claim. But, considering Kaiba maintained his composure and his voice calm and neutral, he was dead serious.

"That's impossible to believe. Dimensional transportation is still just concept." Natasha responded, and frowned when she sees Seto lightly chuckling at her.

"I was like you. I just wanted to be the best duelist in the world but I kept getting involved in events that you can't possibly comprehend. It's the truth, and luckily Diva was defeated and his cube taken away." Kaiba responded, his voice filled with conviction.

Natasha's brow furrowed in disbelief. "And what happened to this 'Quantum Cube?' If it does exist, it will be too dangerous without intense oversight." The redhead reasoned, hoping to receive more potential information from her assignment.

Kaiba smirked. "That's a good point. It's a good thing the cube is kept with the person I trust most." He said before using his other hand to gesture to himself. "Me."

The former KGB agent shook her head. "If such a device does exist…" She began, placing a heavy emphasis on 'does,' "…what would you possibly gain from it?" The agent asked, still not believing this entire discussion.

Seto's smirked lessened into a firm line on his mouth, as if anticipating that Natasha will burst out laughing in disbelief over what he will say next. And truth be told, if Natasha wasn't an agent with intense discipline, she would have after hearing Kaiba's response. "I harnessed the power of the Quantum Cube in conjunction with my technology from my space station to open a portal to the afterlife."

It was at this point that Natasha's patience with this entire conversation reached its breaking point considering how ludicrous this narrative is becoming. "That's literally impossible and one of the most ridiculous sentences I've ever heard. Even if I were to believe that you somehow entered the afterlife, why go there at all?" She said, her stoic mask beginning to crack at hearing these non-sensible claims and is beginning to wonder if the billionaire is just making things up as he goes.

Kaiba remained silent for a few moments, with Natasha noticing his demeanor changed once again. Only this time, the redhead noticed a combination of sadness, anger, and pride all radiating off him as he recounts…something. "To settle a score with an old rival." Kaiba responded, his response softer in tone than before.

Though the moment ended as Seto sharply regained his focus, his pistol still aimed directly at her. "Believe me or not, I don't care. I'm telling you the truth. Isn't that what you came here for? To get answers? Well, you got them." The billionaire remarked, lowering his weapon down to his side.

Natasha gazed back in confusion. "You're… letting me go?" The agent asked, unsure what exactly is happening.

Kaiba's cold gaze resumed. "Don't think I'm doing this out of the charity of my good will. I'm a realist; this is a warning. You've got what you came here, so go. And if I see you or any other agent from the Strategic Homeland Intervention Enforcement and Logistics Division trying to sneak in here again…" He paused, and took delight at seeing Natasha's eyes widen at the mention of her organization before reaching into his pocket and pulling out a flash drive. "…I'll dump all your organization's dirty laundry on the web for the whole world to see."

Natasha analyzed the tone of his voice, trying to decipher any sort of sign that this all posturing and a lie. However, it became quickly apparent that Kaiba's threat is genuine. The billionaire's cold smirk never wavered. "I happen to be a good hacker myself, so if I were you and your employer, I suggest you stay on my good side from here on out." Seto remarked before placing the drive away and pulling out a device with a red button. Instantly, Kaiba pressed said device as immediately the entire building blared an echoing klaxon.

Kaiba's smirk retained on his face. "I'd start running. I say you have twenty seconds before my security arrives and the building is in total lockdown. Clocks ticking."

And with that said, Natasha immediately took off from Kaiba's private office, but not before glancing her head to see the billionaire staring back at her. As she resumed her pace to outrun the upcoming footsteps of Kaiba's personal security forces, she was going to have a long talk with Fury about future assignments as soon as she leaves Domino City.

Particularly about assignments dealing with egotistical billionaires.