My Sister the Heroine, and I the Villainess

Melancholy filled the air in one of the rooms of the Noir mansion.

For better or worse, the Noir mansion was always filled with life and joy due to the presence of the energetic mistress of the house. However, a feeling of overwhelming weariness took over the living room.

There were two people there.

One of them was Michelie Noir.

It was a few short years after she had graduated from the Academy. Almost at the age of twenty, she was still a lady squatting in the Noir mansion. She would most likely spend the rest of her life there. As long as her sister was there, she would stay rooted at home, and she made sure it happened at any costs.

The worsening of her sister complex was no longer reversible, but they still lived happily together, so it wasn't much of a problem.

The other person was Charles Noir, the spouse of Chris, who was mistress of the house.

With their relationship as stepsiblings unknown to most, Michelie and Charles were very much alike. Not only in semblance, but in terms of character as well. Thus, they didn't get along at all.

And yet these two sworn enemies were spending time together.

At the current moment, Chris was out running errands, which were spread over the course of three days.

The moment Chris left the house, a fierce battle broke out between them, causing an overwhelming amount of trouble for the servants. Their fight lasted for about two days, until they ran out of breath.

They were fighting over the same reason.

"Big sister… isn't here……"

"No, she isn't……"

Precisely because they both loved Chris and were competing with each other, the fact that Chris wasn't there made them lose their will and determination.

Thus, they ran out of energy, and were lounging about listlessly.

It was supposed to be the day of Chris's return. They were on standby in the living room with the front door of the mansion in sight, waiting to welcome her home.

Their thought process was basically the same. They looked at each other, consumed by lethargy and weariness.

While drinking a cup of black tea, Michelie thought:

I wonder if I'll hit Charles if I throw this plate like a saucer.

Charles thought:

If she throws that plate at me, I'll hit her face with this half eaten cake.

Their thoughts remained exactly the same from when they were five years old.

As they came up with such helpless thoughts in such a helpless mood, they heard the front door opening.

Chris was home. Their expression changed.

They became so cheerful that one would find it difficult to believe they had been so helpless.

Charles was the first to stand up.

In terms of physical capability, Charles was no doubt the better. Even if they became old and started from the end of the hallway, Charles would probably still be first.

Of course, Michelie would never allow that.

"Oops, my hand slipped."

"Huh?!"

Michelie said monotonously while dragging the carpet at her foot with full force.

Charles fell forward.

Serves you right. Michelie's face was filled with glee as she ran past Charles, who tumbled pathetically. She would perform her duty as a sister in welcoming Chris home.

However, Charles was no ordinary person. Rather than being the only one to fall, he dragged Michelie down with him by pulling on her skirt.

"Wha-?!"

This was the perfect example of a situation in which they could hardly bother maintaining their own appearances.

As a result, they fell on each other splendidly.

"……What are you doing? Are you such a child to grab a lady's skirt?"

"I couldn't help it because a certain someone caused me to lose my footing."

Of course, there were no indecent intentions between the two of them.

Michelie, who ended up on top of Charles like he was riding a horse, thought that it was the perfect chance to take a mounted position and hit him. However, she also considered the possibility that Chris would come in and see her hitting Charles, so she hesitated.

It was the same for Charles, who simply wanted her to get off because she was heavy.

"You two! Your mistress Christina Noir is ho-"

The beautiful woman with black hair swung the door to the living room open.

Her eyes were sparkling with energy and generosity. It was as if anyone who looked into them would be filled with the same energy. Above all, her smile was most charming.

It was a priceless smile of intelligence and purity.

That smile stiffened as she saw Michelie on top of Charles in the living room.

"Big sister, this isn't what you th-"

Just as she tried to explain the situation, it dawned upon her and Charles that it looked like they were having an affair. They became silent.

"……"

Chris closed the door while maintaining her stiff smile.

"-!"

"Argh!"

Michelie suddenly stood up, kicking Charles in the stomach. Ignoring his cries of pain, she ran down the corridor to chase after her sister.

"Big sister! I said it's not- She's gone?!"

Despite her upbringing as her lady, Chris was also a physical brute. She had disappeared from the mansion in a flash.

________________________________________

On that day, Surfania Calibrachoa was surprised to see the lady dash into her room.

"-Then, Michelie and Charles were… there… hug… hugging each other……!"

Her old friend Chris was talking almost intelligibly, looking as if she was about to cry.

She sobbed and choked on her words, but Surfania was able to deduce from her minced words that Charles and Michelie were having an affair. Even for her, it was difficult to imagine such a situation.

"Huh, I see."

"*sniffle*……"

They were the least likely pair in the world. Even if they were the last remaining humans, they would most likely kill each other first. In fact, they would be the most likely cause for the extinction of the human race. In which case, it would no doubt be caused by a war over Chris.

Thus, Surfania had only one thing to say.

"That's stupid. They probably tripped over each other, ended up in that mounted position, and were just about to hit each other, no?"

"Of course not!"

Even though that was roughly what happened, Chris refused to admit that Michelie and Charles - especially Michelie - would do such a thing. Chris's judgment had always been clouded because she thought too highly of Michelie.

"Hey! Let's talk about more serious things. What should I do now?!"

"I think everything will be over once you go straight home and say 'I'm home'."

"I said I was being serious, right?!"

"Oh, sorry, Chris."

For once, Surfania had been listening and giving her advice in all seriousness. She apologized coolly.

"I have plans to see a play with Leon today. I don't have time to play along with any more of your nonsense."

"You traitor!!!"

Chris grabbed Surfania's shoulder and stopped her just as she was about to leave.

"Why are you so unreliable as a friend?! Leave that worthless Leon aside! Take me more seriously! I'm the one thinking normally, so I'm more important, right?!"

"Sorry. I don't have time to play along with a worthless lady, and I never thought the day would come when you would think of me as unreliable as a friend."

"Why are you saying this?! There's no one who takes friendship more seriously than I do!"

Surfania frowned at her confident words.

She posed a question to Chris.

"Whose situation would you prioritize? Mine, or that wicked sister of yours?"

"Michelie's, obviously!"

"Farewell."

Surfania had seriously thought about canceling her plans and apologizing to Leon depending on her response, but she squinted at Chris in displeasure and flatly said goodbye.

It felt just like a girl breaking up with her useless boyfriend.

"Hey! Y-you're seriously leaving?!"

"Isn't it obvious? Oh, hurry home after I leave. It'll be a problem if you remain here. ……Oh, Chris. Allow me to say a word of thanks."

She turned around, gorgeously showing her cold looks to Chris.

"This will make a good conversation topic between me and Leon. Thank you."

The look in Surfania's eyes seemed the most pleasant recently.

________________________________________

Michelie and Charles remained in the Noir mansion.

They were playing a board game.

"Where did Chris go?"

"Miss Surfania's place."

"She'll probably chase her back here."

"Yeah."

"How long?"

"It won't take long."

Since Chris had left, they decided and acted swiftly.

After Chris had ran off so quickly that she couldn't be stopped, they deduced that she had gone to Surfania's house, where Surfania would chase her out while acting nonchalantly. Thus, they waited in the mansion for her return.

They would rather see the world end than have an affair. They agreed that they should clear up the misunderstanding as soon as possible, and finished the conversation in just a few words.

And thus, they were having a match over a certain bet.

"Win or lose, no hard feelings."

"Of course. Well, I'm not going to lose."

"Hmm?"

They were frighteningly agreeable only in times like these. One of them would definitely stab and kick the other in the back halfway, but that was a different matter. In any case, their thought process was exactly the same.

They were moving their pawns while making their conversation as short as she could.

Michelie had self-confidence when it came to this board game.

It was Chris's favorite game after all. She had learned how to play from Mariwa's lessons, and was almost on Chris's level.

Also, she knew Charles's level of skill. It was just about average.

It was an early game with standard moves, but Michelie's expression changed halfway.

Due to Charles's initiative, the board became perplexing to Michelie, who kept playing without being able to read her opponent's intentions. The chances looked bad for her. Even as she kept putting up resistance, she was unable to regain her formation, and was checkmated.

The winner Charles asked Michelie cheerfully.

"So, how many days?"

"……One night."

"Are you stupid? One week."

"Huh? You kidding? Half a day."

"No way. Five days."

"Impossible. One day."

"It's about time to think about how to get along in the world, Michelie. Four days."

"……Tch. Then, three days."

"Fine, three days."

Thus, they finally agreed on the number of days in order to solve the problem.

________________________________________

"I- I'm home."

"Welcome home, Chris."

Charles was the one to welcome Chris back to her own mansion.

Surprised that he was the only one here, Chris took a glance around the area.

"Huh? Where's Michelie?"

"She's dead."

"What?"

"Hm? I didn't say anything."

She was sure that she had heard him say something, but now wondered if she was mistaken.

Still, it was rare to see Charles alone. There were usually more people to greet her when she came home.

Charles showed Chris a wide smile.

"Michelie has gone to Miss Toinette's place. I think she's staying there for three days."

"Mariwa's place?"

This was a weird timing.

Blinking her eyes, Chris thought about what happened earlier in the day, and began sulking.

"H-hey, Charles. Um, how should I say this……"

"It's about what happened in the day. It's alright, I'll explain everything."

"I- I see. I'm okay. I knew that such a fate existed…… so I understand. When it comes to that, be sure to tell me."

"Yeah, you don't get it at all. Nothing's happened. It's alright. The only wife I love is none other than you, Chris."

Chris was being unnecessarily depressed. Charles took her hand to stop her from running away.

"It's alright. I'll make sure such a misunderstanding never happens again."

He kissed her hand without a hint of embarrassment.

"We'll be alone, together, for three days."

Charles happily announced the number of days he won from Michelie, causing Chris's face to tinge red with embarrassment.

________________________________________

Meanwhile, Michelie had reached Mariwa's house.

"What happened all of a sudden? And the reason you came was because you wanted to play board games."

"I am so deeply frustrated that I lost to Charles."

The sparkle in Michelie's eyes had gone.

When Chris misunderstood the situation, Michelie and Charles played a match to decide who would get the role of cleaning up the misunderstanding, as well as the privilege of consoling Chris. The condition was that the loser would have to leave the mansion for a while.

And she lost.

To Charles, of all people.

Over Chris, of all things!

"I was so sure I would win……"

It was truly regrettable for her.

She was the one who had proposed playing the board game in the first place. Because she had confidence in herself. And Charles had accepted. Because he, too, had confidence in himself.

Michelie remembered the difference in their abilities when they were students, and clenched her teeth.

Did he keep practicing after he graduated from the Academy? Or perhaps- there was also the possibility that he had always concealed his abilities since they were children.

That he had always deceived everyone and saved his victory for times like these, when it was all or nothing.

"It takes days, even months, to improve on the opening moves. You are conceited to think that you could win after not doing your research on your opponent for years. ……Well, I shall leave my collection of recorded games with you, so read them as you please."

"Ugh…"

Michelie couldn't argue against Mariwa's sound argument, and took the book in her hands.

Having known the reason for Michelie's visit, Mariwa let out a long sigh.

"Sigh. And I had thought that you came here out of consideration for them……. In fact, you should move out of the Noir mansion-"

"Aah, I can't hear you! I can't hear Miss Mariwa's voice at all!"

Michelie covered her ears and protested.

Mariwa sighed again as Michelie's behavior reminded her of her old friend.

________________________________________

It was about ten months and ten days since that day.

The heads of the Noir house bore a son. Thus, their successor became included in those happy days that followed.