An Experiment with Unexpected Side Effects

Jingle!! "Goodbye!" After seeing off the day's final customer, I gazed at the scenery outside that had already grown dim and hung the Closed sign before cleaning the restaurant interior. I usually cleaned up after closing anyway, but today I scrubbed everything with unusual vigor. After all, I still had one more guest to receive.

'I'll need to cook right away, so I'll leave the kitchen as it is... and just get the ingredients ready in advance.'

While cleaning with my heart strangely pounding in my chest, someone entered the store despite the closed sign. "Excuse me..." The person who stepped inside with a noticeably more reserved attitude than she'd shown during the day was, of course, Astra. However, the instant she entered, there was a fleeting moment when I almost didn't recognize her. And that was because.

"Your clothes... have changed?"

"Y-yes. I didn't want to draw too much attention, and just in case."

Since the only version of Astra I ever saw was her hero form, the only outfit I'd seen her wear until now was the suit she used as a hero. The special-material clothing the Hero Association produced to enhance each hero's symbolism. But the Astra who had just walked into the store was wearing ordinary casual clothes instead of that hero suit.

"I picked something that would be fine even if it got torn. And if possible, something... loose-fitting."

As she said, the clothes Astra wore were a slightly oversized hoodie. It was a plain, unadorned garment, but because this was my first time seeing her in civilian attire, even that simple outfit seemed to make her beauty stand out all the more.

"Please have a seat and wait for now."

"Yes... But. Even though it was my suggestion, are you really okay with this?"

When I pulled out a chair and offered it to her, Astra sat down hesitantly and asked for my confirmation once more.

"It was my idea, but in the end this is your ability, Mr. Siwoo, so the choice is yours. You might be perfectly fine simply living without using it at all, without knowing anything."

"Huu....."

"The more you learn about it in detail, the harder it might become to hide..."

The reason Astra had come to my store at this late hour was the proposal she'd made to me earlier that day. She wanted to experience my ability once more and properly measure the resulting changes this time. She had spoken of the possibility of permanent growth in Superhuman Power and suggested we check together whether any other unexpected effects might appear.

"...No. I think it's better to verify everything properly while I have a helper like you, Miss Astra."

Just as Astra said, the more I learned about my own ability, the harder it might become to conceal it the way I'd originally planned. But even taking that into account, after hearing there might be another possibility hidden within my power, I simply couldn't let it slide without confirmation.

After all, this was an ability that resided inside me, so the desire to understand it in greater detail had always been there.

And. On top of that... 'I said I'd hide it and never use it on anyone else, but... the moment I already used it on Astra, there's no telling when I might end up using this ability again.'

Until recently, even after gaining this ability, I had resolved to simply conceal it and live an ordinary life. But witnessing a giant monster appear right beside my store had made me realize something. No matter what mindset I clung to, a single suddenly appearing monster or villain could shatter the daily life I wanted to protect in an instant.

This world was that kind of place. A world where heroes maintained the peace, yet ordinary people without superhuman powers could easily get caught up in incidents and lose their lives.

'So if I face a situation like this again... would I really be able to refrain from using my ability?'

Like today, I might desperately bestow buffs on Astra or other heroes to survive, or perhaps research into the ability could reveal ways for me to grow stronger myself.

'For that reason too, I need to ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠properly study the ability I've been roughly ignoring until now.'

In that sense, the fact that a trustworthy hero ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠like Astra had stepped forward first to suggest investigating my ability was an opportunity I couldn't miss. It had reached the point where I should have been the one begging her to help me research it.

Since I'd already tested the ability on myself many times, researching it would inevitably require help from another person.

"But... are you sure you're all right with this, Miss Astra? As you've already experienced, my ability comes with side effects..."

"Eep...!"

The moment I mentioned the side effects, Astra's face flushed bright red. No matter how casually she tried to act, the experience of having her bare breasts massaged by a stranger must have left a deep imprint. After going through that, was she truly prepared to receive my buff again?

"As I told you before, even when I used it on myself the type of side effect changed every time. I can't control it, either. There's a chance it could be similar to last time, or even more severe..."

The Breast Expansion side effect from before had been quickly forgotten amid the intense resolution process, but objectively speaking it had been an absolutely dreadful one, hadn't it?

"I... I know that."

Certainly. The side effects seemed frightening to her as well. Astra trembled for a moment, hesitating, but she soon shook off the fear and steeled her resolve.

"Because I want to know the exact cause of the changes that happened to me. And also..."

"Also?"

"...Never mind. I'll tell you later."

Why did she have to vaguely drop something she wasn't going to explain? It made me curious, but I had no intention of pressing her.

"Very well. Then... let's begin right away."

After locking the store door securely and drawing the curtains over the windows, I headed for the kitchen. Although we called it verifying the ability, mine wasn't something I could ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠activate with a snap of my fingers. It could only manifest through the medium of cooking. Naturally, preparing a meal was essential for the experiment, and I had already decided on the menu I would serve Astra.

"I'm fine with anything..."

"No. Since you're eating anyway, it's better to have something proper."

As someone working in the food industry, I also held the conviction that I couldn't serve anything less than delicious. In that spirit, the menu I had chosen was salmon steak. It didn't take too long to prepare, and depending on the side ingredients and sauce it could offer a variety of flavors.

I took the salmon I had wrapped in kelp and aged in advance out of the refrigerator and gently patted it dry with a kitchen towel. I heated olive oil in the preheated pan, placed the salmon skin-side down, and began searing it.

Sizzle. Sizzle.

"Wow..."

Listening to Astra's admiring sigh with satisfaction, I mashed the pre-boiled potatoes, mixed them with milk, and seasoned them with salt and pepper while bringing the mixture to a simmer. I plated the simply prepared mashed potatoes first, then added a small drizzle of gravy sauce on top for accent. Meanwhile, I dropped butter and rosemary into the pan where the salmon skin had crisped nicely. As the butter began to bubble, I spooned it over the fish to finish cooking the flesh.

Once the salmon steak was complete, I set it atop the mashed potatoes and gave it another light drizzle of sauce.

'Tartar sauce would be safe, but...'

I had prepared the sauce to suit my own palate, a sweet-and-savory blend based on soy sauce and garlic. Having observed Astra's taste preferences during her visits as a customer, I had a strong feeling this combination would appeal to her.

Buff Bestowal.

At the moment the dish finished, I used my ability without missing a beat. An inscrutable energy seeped into the food. Come to think of it, this energy that appeared whenever I activated my power—could this be the so-called Superhuman Power?

"Please enjoy."

"Ah..."

Even though the meal itself wasn't the main objective, the rich aroma of butter rising during the cooking process must have stimulated her appetite. Astra stared at the dish as though spellbound. After studying the perfectly seared salmon steak that glistened with oil, she began eating as if in a trance the moment I handed her a fork and knife.

Clink.

The fish flesh tore easily along its grain yet retained a pleasing elasticity. Soaked in sauce, it slipped into her mouth.

"It's... delicious. What is this sauce? That subtle spiciness really cuts through the richness..."

"I used quite a lot of garlic while making the sauce."

It seemed I had consumed a great deal of garlic in my previous life. Although I couldn't recall it perfectly, the habit had apparently soaked into my body. As a result, my dishes tended to feature plenty of garlic. Fortunately, it appeared to suit Astra's palate.

"Mmm..."

She made quick work of half the salmon steak, then continued eating in silence while refreshing her palate with the gravy-topped mashed potatoes. By the time she emptied the bowl, she seemed to realize how frantically she had eaten. Looking slightly embarrassed, she wiped her mouth with a napkin.

"Was the taste all right?"

"Yes... It's always delicious."

It was quite satisfying as a restaurant owner to see a customer enjoy the food so much, yet today something far more important than taste evaluation remained.

Crackle!!

"Ah..."

The moment Astra finished eating, the electric current leaking from her body grew steadily stronger until it flashed with alarming intensity.

"This is... stronger than last time...!"

Unlike the previous occasion when I'd only given her a single bite of what I was about to eat myself, this time she had consumed an entire ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠properly prepared serving. Even to my untrained eyes, the amplification of her power looked noticeably greater than when she had fought the monster before.

Still, since there was no battle to fight at the moment, she focused intently on the changes in herself that she had been forced to overlook last time due to the urgency of the situation.

"Not only the output of my ability... my senses and strength have increased as well. And this is... recovery power? My mind feels clearer, too..."

She closed her eyes and carefully observed the transformations within her body, then calmed the wildly rampaging current and drew it back inside. Even though her suddenly enhanced power could easily have gone out of control, she managed it as naturally as if she were wearing perfectly fitted clothes.

This is impressive too. Buff-type ability users exist from time to time, but... I've heard those powers are usually difficult to control, like wearing clothes that don't fit properly.

While admiring the buff's performance, she checked the time. After roughly ten minutes had passed, she felt the power gradually draining away. In the process she gathered several pieces of information about this "buff," but for now she decided to focus on something else.

Jiggle!!♥

'Eep...!!'

Along with the sensation of the buff dissipating came a strange new feeling. It originated in her chest, and Astra realized the hoodie that had felt comfortably loose only moments ago was now tightening against her skin. She experienced the change that had occurred in her body.

'Again?'

The sensation of her breasts—which had only been around a C-cup—swelling even larger. Was she afflicted with the same Breast Expansion side effect as before? That's what Astra thought, yet she sensed that something felt slightly different from last time. Her breasts felt heavier... as if they were filled with something...

Drip!!

"...Huh?"

The moment she focused more intently on that sensation and tried to identify the change, Astra felt her chest area growing strangely damp and let out a dazed sound.

Watching the transformation overtake her, I absorbed the information about the side effect that had appeared in my mind.

It came with additional information, not merely the side effect and its release condition.