I Was Reincarnated as the Prince in a Villainess Story, so I’ll Use My Cheat Knowledge to Create a Noble Lady Harem and Make Them All Happy - 2

Chapter 2: The Reincarnated Prince Dreams of Sewers in Another World

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When he opened his eyes, he saw a ceiling. No, to be precise, it was something that resembled a ceiling. A curved surface coated with what looked like plaster, framed with gold decorations forming geometric patterns. Illuminated softly by indirect light, it shimmered faintly. This was definitely not the ceiling of the public housing apartment he knew.

His thoughts were muddled. His head felt hazy. His body felt heavy. No, small. When he tried to move his limbs, his squishy, pudgy arms wobbled awkwardly, and they were far too close to his face. When he tried to make a sound, what came out was a strange, whimpering cry.

“Ah…”

N-no way…

His mouth wouldn’t move the way he wanted. He could think, but he couldn’t speak.

An unfamiliar room. An older woman leaning over him. She wore a navy-blue dress with an overly elaborate frilled collar, something that made her look halfway between a maid and a nurse. She brought her face close with a tender, loving smile.

“Well now… Your Highness, are you awake?”

Your Highness…?

The moment he heard those words, a chill like cold water ran down his spine.

Whoa, whoa, whoa, whoa, whoa. Hold on. Calm down, me.

Calling out to himself internally, Valis—no, Ryuusuke Sakagami (age 35, single, civil servant)—was quietly panicking inside the body of an infant only a few months old. He was conscious. His memories were intact.

When he closed his eyes to check, he could clearly recall memories of last night. Valis had been sitting in his room, still in his work clothes, drinking canned chuhai, and reading a summary thread about erotic visual novels. The topic was “The Recommended Villainess-Type Stories.”

After that, before going to bed, he had casually read a web novel. Its title was──

『The Crown and the Cage of Purity』

And now, this situation…This extravagantly ornate, Western-style room… The well-trained servants… Everyone addressing him as “Valis-sama” and in the mirror, he saw a beautiful infant with silver-gray hair and blue eyes staring back at him.

Ah, crap. Valis, you’ve really done it this time.

Apparently, Ryuusuke Sakagami had been reincarnated as First Prince Valis Alveria, a character from that very novel.

『The Crown and the Cage of Purity』

It was a medium-length web novel that had gained popularity for its easy-to-read prose and its charming villainess heroine, Reina. The story was told from the heroine’s perspective. The protagonist was Reina. Supporting her was the reincarnated margrave’s daughter, Feril.

Meanwhile, the First Prince, Valis—now Ryuusuke—was portrayed as a “tragically handsome” man. He was deceived by political enemies, scorned by his villainess fiancée, and ultimately exiled from the kingdom.

You’ve got to be kidding me.

In his previous life, he had reached thirty-five without ever being close to a woman. Half of his attraction to “villainess” stories came from his masochistic wish to be insulted by a beautiful woman. The other half came from a pitiful desire to be forgiven in the end. But now that he had been reincarnated…

I’ll live a better life this time. Better than my past self, no matter what.

He could do it. Because…

I have my past-life knowledge cheat to rely on!

The kingdom’s water and sewage systems were practically primitive. No mention of such things even in the original novel. No sanitation, no plumbing, no concept of hygiene. The nobles burned incense in their toilets, and commoners used cesspits. For Ryuusuke, who had worked ten years in the Department of Sewage Management as a local government official, there could be no world better suited to his expertise.

Heh… Let’s do this.

The moment he grinned to himself…

“My, Your Highness… Are you smiling?”

The wet nurse blushed and clasped her hands together in delight.

No, no, you’ve got it wrong. That’s just a nervous twitch.

A few years later, as part of his early education, Valis began taking private lessons. Geography, history, ethics, magical theory. Though his body was that of a child, his mind was that of a thirty-five-year-old modern man. Everything felt dull. Every time the tutor wrote on the board, his inner thoughts burst with silent commentary.

Seriously? ‘Purifying water with magic’? Just integrate that into the sewer system and boom—instant infrastructure revolution. ‘Blessing of holy water’? That’s basically a water-treatment system waiting to happen. We could build mana-powered pumps for this.

Before long, the adults around him began whispering.

“The First Prince possesses extraordinary intelligence.”

“He seems blessed by the gods themselves.”

“Surely, he will bear the kingdom’s future.”

Hmph. He didn’t need to be told twice. That was already his plan. And then… One day, she appeared in a corner of the castle.

Golden ringlet curls. Azure eyes. A dress of impeccable tailoring, radiating both grace and arrogance. Reina Agreia, the marquis’s daughter. She was the “villainess” of the original story.

Despite it being their first meeting, she looked him over as if assessing his worth and said boldly.

“So, you’re the one who’s to be my fiancé?”

At that, Valis was momentarily speechless. Just like in the original, she was haughty, confident, and yet already refined in every gesture, even at her young age. And as he looked at her, Valis thought from the bottom of his heart.

This girl must never become my enemy.

No, he would make her his most trusted partner.

Reina Agreia… Amarquis’s daughter of the highest rank, and a future queen candidate. But in the original, she fell from grace as the ‘villainess,’ driven to ruin after insults and condemnation… She was rescued by the reincarnated margrave’s daughter Feril, which in turn led to the foolish Prince Valis’s exile.

Before his young fiancée, Valis quietly began his observations. Her hair’s luster. Her posture. The way she chose her words and deep within her eyes, a loneliness she herself hadn’t noticed.

Even at this age, Reina was already protecting herself by pushing others away. Her fall into villainy in the original story had clear causes: the crushing weight of queenly education, the pressure of purity ideals, emotional distance from an unloving fiancé, and the isolation of high society. But now, Valis knew her future.

“…I’m Valis. Nice to meet you, Reina.”

At the time, Valis was five. She was six. When he extended his small hand, Reina frowned for a moment, but…

“You at least have manners. I suppose that’s… Acceptable.”

…She then gently took his hand. At that moment, Valis knew. He would make this girl happy. He would never become her enemy. As the years of education passed, Valis steadily gained the trust of everyone around him.

Teachers praised him.

“His Highness shows exceptional aptitude in magical theory.”

Vassals murmured in awe.

“To speak of politics and economics at such an age…”

Of course, that was only natural. Valis carried thirty-five years of real-world experience and had read over a hundred isekai light novels. In terms of knowledge, no one in this world could match him. But the real challenge lay in practice.

This world had no concept of hygiene. Even the royal family used chamber pots, and bathing was a once-a-week affair. So Valis set his sights on one goal: the bath.

“If they can heat water with magic, why don’t they have a hot-water circulation system?”

With that in mind, he studied ancient magical archives and learned how to control “mana-driven water flow,” constructing a simple prototype: wooden pipes embedded with magic stones to channel water in one direction. He secretly installed it in his mother’s private bath—the Queen’s own chamber.

“My, what is this delightful warmth…?”

The Queen’s voice of wonder while soaking in the bath spread through the castle the next day. The bathwater stayed warm, never stale, and the smell vanished. Wastewater drained automatically. It was clean, efficient, and comfortable. 

The maids all said.

“It was His Highness’s invention!”

“They say it’s based on ancient magical archives!”

The King took notice of his invention.

“Interesting. Perhaps we should install this not only in the palace but in the barracks as well.”

Yes, first step: success. Suppressing a satisfied grin, Valis began planning his next move. Not long after that… As part of their studies, Valis and Reina were sent to the Royal Library Tower.

“Valis. For today’s lesson, I’ll be the one asking questions.” 

Reina declared, her golden curls swaying.

“There’s a rumor that beneath Alveria lies a ruin from the age of the gods. Do you believe it?”

No doubt it was something she’d just learned. Her proud expression was adorable.

Right, that was in the original story too. The ruins of the abandoned city, filled with unresearched magical structures, later used as the enemy’s stronghold in the final act. But as someone living in this world now…

“It’s more useful to assume it’s true. Rather than ruins, it might be remnants of an ancient water and sewer system. Because, you see…”

And from there, Valis began to explain. Drainage paths, water flow, geothermal heat, castle foundations, signs of subsidence. Reina listened in silence, wearing an expression he’d never seen before.

“…Valis.”

“Hmm?”

“You’re a strange one, aren’t you?”

“…Yeah. I guess I am.”

Her eyes seemed to waver slightly.

We’ll change this world. Together.

It felt like an unspoken promise had just been made between their hearts. That night, lying in bed, Valis thought to himself.

His knowledge wasn’t useless and… He wasn’t alone. Reina was by his side.

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