Under skies that seemed to mock the rainy season with their clear blue, Ryosuke walked absently, glancing sideways at the sea, its blue waters shimmering in the sunlight.
Kirie was on his left.
She held an umbrella aloft, looking hot and uncomfortable, but it was she who had requested they stroll through this seaside park.
This park had a superstition: couples who walked hand in hand here would be blessed with happiness. ...She hadn't mentioned it herself, but her actions seemed influenced by that rumor.
But Ryosuke's mind was wandering.
"Hey, are you sure you don't need an umbrella?"
"Mm, yeah... I should have worn a cap instead."
He could only muster such trivial responses.
It felt like a haze, like a mist, had been covering his heart all along. He couldn't pinpoint the cause, but it wasn't a pleasant feeling.
Ryosuke was aware that his ability to act normally without alerting Kirie was both his strength and his weakness.
"Ah, it's really hot. Let's rest in the shade over there... somewhere no one else is."
"I-I think you should stop saying things like that every time..."
Though he was scolding Ryosuke, Kirie-san couldn't help but wince as she started walking toward the woods.
But contrary to their expectations, the benches scattered along the shaded path were nearly full of walkers seeking respite from the midsummer sun. After walking for a while, they finally managed to secure a two-seater.
Still, Ryosuke's mood remained gloomy.
For some reason, thoughts of his family kept surfacing in his mind.
Manaka. Marin. And their parents—
His current mother is his third.
The first... mother abandoned Ryosuke and his father.
According to fragmented information, she's remarried to a father with children and seems happy. The last time he saw her was a few years ago, when he stumbled upon a photo on her social media of her laughing joyfully with her son (...).
The second marriage also failed.
That time, his father was the one to give up. The second wife apparently couldn't fill the void left by the first.
As for his current stepmother, Ryosuke could see cracks in their relationship with his father from an early stage.
It's only a matter of time, Ryosuke thought.
If that happens... Manaka and Marin will become complete strangers to me. What will they do then? Will they try to find someone to replace me?
Nee-san...
She has someone to rely on.
Ryosuke had recently become convinced that she could manage without him. He'd even prepared her for that eventuality.
Marin...
He started thinking about his younger sister-in-law—
Then stopped.
Thinking about her was a waste of time. He could roughly predict what would happen. She would probably remain unchanged.
Ryosuke was skilled at reading people's minds, but his ability was utterly ineffective with Marin—not that he needed it. She didn't even bother hiding her true feelings. And it seemed she had no intention of changing.
"...Ryo-kun?"
He was lost in thought for only a fleeting moment, but it seemed to have left him slightly unguarded.
Kirie tilted her head and gazed at him.
(...)
She's just as oblivious as me, Ryosuke thought. Just like her childhood friend, she hasn't noticed my feelings for her.
"Has Kirie already forgotten him?"
Suddenly, Ryosuke found himself asking a question he hadn't intended to voice.
He knew there was no need to feel competitive toward her—she was someone he shouldn't even be competing with.
"–Huh?"
Kirie looked bewildered.
No wonder. The question was so abrupt, completely out of the blue. There was no conversational flow to support it.
Even Ryosuke, usually so composed, couldn't find a way to cover for his own blurted words.
So.
Ryosuke deliberately pressed further.
"Am I really managing to fill his shoes?"
The words slipped out naturally, a pointless question that made no sense. Even the person being asked would be at a loss.
"..."
As expected, Kirie remained expressionless, simply staring steadily at Ryosuke.
But Ryosuke waited for her to speak.
The time passed in the deluge of cicada calls—probably only one or two seconds, but Ryosuke felt uncharacteristically nervous, so tense he couldn't believe it himself. It was as if the world was coming to an end.
Suddenly, Kirie flung her hand away, forcibly wrenching it free from where it was linked with Ryosuke's.
Ahh, I knew it, Ryosuke thought.
He shouldn't have asked that question. He had lost his right to be her "beloved lover."
Strangely, he felt neither disappointment nor despair.
That's just how it is, I thought, resigned.
But then...
"Ryo-kun."
"Huh...? Ow!"
Kirie pinched the tip of Ryosuke's nose with her other hand, with surprising force.
"Ow, that really hurts! Stop it!"
"Shut up."
I wanted to shake her off, but her fierce demeanor intimidated me, leaving me at her mercy.
"I did like Kazuki, that's true," Kirie said, her voice surprisingly calm despite the force in her grip.
"After he dumped me, you swooped in, Ryo-kun."
"..."
"At first, I hated you... You're so flippant, I can't tell what you're thinking, and you probably make tons of girls cry."
The continued pain made Ryosuke think he might start crying if this went on much longer.
"But since I've fallen for you, there's nothing I can do about it. That's the kind of Ryo-kun I've fallen for. So if you ever call me a substitute or anything like that... I'll be seriously angry this time, okay?"
"Are you serious right now?"
"If I get serious, I'll make it hurt even more."
"..."
"Got it?"
"...Got it."
"Right."
With that, Kirie casually let go of him.
Ryosuke, still grappling with an indescribable emotion, gently touched his stinging nose.
"Ahahaha!"
"What's so funny?"
"I've never seen you make that face before. Ryo-kun, you're still as unreadable as ever. You probably weren't going to say anything anyway, but you owe me. You're responsible for making me fall for you—"
After saying that, she seemed to suddenly recall everything she'd just said.
"Uh, um... that's what I meant! I'm just gonna... go to the bathroom for a minute..."
She flustered to her feet and hurried away.
Ryosuke watched her go, his mind going blank.
"..."
When he came back to his senses, he pondered for a moment before pulling out his smartphone. With a scheme forming in his mind, he dialed a number—
*****
In the dimly lit living room, a smartphone vibrated with an incoming call.
"...This is a good spot, though."
Marin, seated on the sofa, muttered under her breath before picking up the phone and glancing at the display.
"..."
Her eyes lit up instantly. She tapped the screen to answer.
"Marin?"
The other person spoke.
"Hello. It's been a while, Nee-san."
Marin replied with a cheerful tone.
"Sorry to bother you. Are you busy?"
"No, I'm alone right now. I was watching a video about insects around the world. It was about neon-colored dragonflies molting... but videos don't run away, so I'm not busy at all."
"...Right."
Marin paused the video playing on the living room's big-screen TV and settled back on the sofa.
"So, what's up? Why did you call me, Nee-san? You never come to visit anymore."
"That's because—"
Manaka trailed off.
Marin had no intention of blaming her.
In fact, Marin was in a buoyant mood, wiggling her toes in her cross-legged sitting position as she thought about the person on the other end of the call, smiling innocently.
Silence seemed to be painful for Manaka, but for Marin, it was pure enjoyment.
"Um, about Ryosuke..."
When Manaka finally brought it up, Marin instinctively replied,
"You mean my older brother? Don't you care about me at all?"
"Ugh..."
This wasn't meant as an interrogation, but Manaka still apologized.
Hearing this only made Marin even more pleased.
"So? What's wrong with your brother?"
"...Marin, about Ryosuke and me..."
"Huh? Oh, you mean the sex? He went there the day before yesterday too, didn't he?"
"...Did Ryosuke tell you?"
"No. I just smelled your scent on him."
Manaka seemed to shiver at Marin's casual remark, and another silent moment fell between them.
She probably wasn't trying to hide it either. No, she wasn't even trying to hide it, Marin chuckled inwardly.
"I think I'll just let things end with Ryosuke."
"Why's that?"
"I think he feels the same way... He's got a girlfriend now."
"I see. Kirie-san, then?"
Marin had also sensed a recent change in her older brother's demeanor.
"So you're stepping back?"
"Actually..."
"Your brother can be scary sometimes."
"Huh?"
"Ah, no, not in that way. I don't think he's that possessive. He wouldn't go crazy with jealousy or anything like that."
At least, not towards Manaka.
Marin kept that thought to herself.
"That's not it. Older Brother can become anything he wants, can be liked by anyone. I'm so jealous. Meanwhile, I'm living a life where I can't seem to stop getting hurt."
"..."
"But if I were to change completely... if I were to start thinking of only one person... it terrifies me. Would I truly love them, or would I destroy them? Older Brother, you're extreme sometimes."
"I... understand," Manaka replied, her voice carrying genuine emotion.
For the first time since arriving here, it seemed the sisters' hearts had finally aligned.
That's what Marin thought, but then...
"But if Ryosuke were trying to become like that, I would still do it for Ryosuke's sake—"
Manaka said something completely off the mark.
So Marin immediately denied it.
"For Older Brother? I don't think that's it."
"Huh?"
"Isn't it because Nee-san already has what she wants?"
"W-what are you talking about...?"
Manaka stumbled over her words, clearly confused by Marin's statement.
"I mean, Nee-san can already be happy."
"I... I don't understand..."
"Really? Are you serious? She already knows, don't you see?"
Marin patiently explained to her sister, who still seemed oblivious.
"Nee-san learned something incredibly pleasurable, didn't she?"
She had a fiancé—a man she'd been dating since their school days.
"But whenever she's with him, she can't help but remember... that the best sex she ever had was with Older Brother. Being with the one she loves while yearning for someone else—that forbidden thrill is what Nee-san craves, isn't it?"
"N-no... that's not it..." A pained voice came from the other end of the line.
"Older Brother noticed that ages ago."
Manaka must have noticed it too.
But she turned away.
"Well, as long as you two were happy, I guess it's fine. But if Nee-san is serious about quitting now, that's understandable too. If Older Brother has found another kind of happiness, I'll support that. Of course, I'll always care about Nee-san too."
"Marin..."
Manaka's voice trembled.
"W-why are you so calm about this?"
"Huh? I've always wished for happiness. I want everyone around me to be happy. Surrounded by happy people, I just want to be happy too... Sounds childish, doesn't it?"
"..."
I heard her gasp, and then the call ended abruptly.
"...Huh? What a shame."
I wanted to talk more.
Marin thought of her sister and sulked, flopping onto the sofa.
But Manaka will probably contact me again soon.
She'd acquired something else now—the despair of having her true, ugly heart exposed to her own younger sister. To a future already filled with the bittersweet thrill of continuing her engagement to Mirai, she'd now added this vivid, painful realization.
And yet, Marin was glad to be near Manaka again.
Even if they were physically apart, no longer living under the same roof as before, that was enough to make Marin happy.
"..."
Suddenly, Marin found herself reminiscing.
Back when our new family was formed.
When my mother remarried and I gained a stepbrother.
By then, Manaka was already dating her current fiancé. For Marin, who had always supported the two of them just as she did now, Ryosuke was an interloper who appeared out of nowhere.
What if he ruins their relationship and brings misfortune upon them?
The thought made it inevitable that Marin would view Ryosuke as an enemy.
Before long, Manaka was drawn to him, and Ryosuke reciprocated. It didn't take long for them to become physically intimate.
Contrary to Marin's expectations, Manaka's relationship with her lover didn't fall apart. Instead, after Ryosuke left, Manaka and Ryosuke remained bound together in her room.
Marin grew envious of her sister's double happiness, while at the same time, she began to admire Ryosuke.
These feelings developed naturally, and as she grew older, they blossomed into age-appropriate romantic feelings:
Even as a man...
But she never intended to confess them to Ryosuke.
In her sister's room, the two engaged in lewd acts.
Or in Ryosuke's room, where he took in a motley collection of girls and relentlessly pounded them with pleasure.
For Marin, it was enough to simply be "given a share" of their happiness. The mere thought of her beloved being happy with someone she also loved...
"...Ngh... Ah..."
Her thighs, rubbed raw against his, throbbed pleasantly.
"Mmm, haa... This won't do. I need to calm down. Let's watch some videos."
Returning to her observation of insect ecology, Marin thoroughly enjoyed the experience before her thoughts began to wander.
To make my older brother happy, I suppose I should...
"Kirie-san, then..."
Marin picked up her smartphone again and contacted her.
And then...
"One more person, right?"
Her slender fingers glided across the touchscreen as she sent a message. All for the happiness of her beloved and the people she cherishes most.