The Hero Became The Son of The Demon Queen

"That's enough. Just right."

The boy rose from his chair and approached her. Then, he extended his right hand, infused with mana, towards her lower abdomen.
His fingertips were warm. She bit her lip at the warmth against her stomach, which had felt cool. She stopped the moan that almost escaped her lips unconsciously. If she had let it out, she thought it would have been a much more coquettish moan than the ones before.
"Hmm. Good."
The thought crossed her mind: what kind of magic was it that he had placed his hand on her lower abdomen for?
At the same time, he chanted a magic spell. Only then did she realize that the mana in his right hand wasn't gathered to kill her, but to use this magic.
Just as she was about to think she was disqualified as a mage for not being able to distinguish between offensive magic and other types due to fear, the short incantation ended, and the magic seeped into her.
"Aaaahhhhn─!!"
A moan escaped from deep within her throat before she could even hold it back.
"Aaah! Aahn… Aaah!"
An unknown sensation, emanating from deep within her stomach, engulfed her entire body.
For a moment, her mind went hazy, and she almost lost strength in her arms that were holding up her skirt, but she somehow managed to maintain her grip. Whether it was because he liked her attitude or because he was satisfied with the successful casting of the magic, the boy nodded with a pleased smile.
"…Uuunnnh…♥"
She didn't have the luxury to slowly decipher the meaning of his expression.
She had to focus on enduring this strange sensation flowing through her body.
She bit her lip so hard that it bled. She felt her mind clear up a little with the taste of blood. Perhaps it was a mage's instinct, but she tried to figure out the identity of the unknown sensation.
Her body temperature rose, her lower abdomen throbbed, and her chest and genital area tingled.
'…Ah.'
She belatedly realized that it was sexual arousal.
It reminded her of the time when she was a child, when she had mistaken her teacher's hidden book for a secret manual and ended up masturbating for the first time after realizing it was an erotic book.
Although she had missed it due to nervousness, the demon had clearly said that this magic had charm magic as its base. Charm magic made sense. Magic that seduced the mind and aroused the body.
But it was strange. How could he, a man, use charm magic, which was a characteristic of succubi? However, she couldn't ponder this question for long, as she couldn't handle the rising excitement.
Pleasure traveled through her blood vessels, making a full circle around her body and finally reaching her head. As if there was a hole in the top of her head, something burst out from her head.
"Ah, ah… I can't… Aaah!!"
Her head tilted back. Her toes curled involuntarily, and her hands tightened, crumpling the hem of her skirt. Her vision sparkled as if fireworks were exploding before her eyes.
She finally came to her senses after wriggling her body a couple of times.
However, she still felt exhausted. It wasn't just fatigue, but she felt sleepy as if she had used up all the mana in her body.
"Haa, haa, haa."
"Good job."
"Ye, yehe."
She responded to the boy's praise with a slurred tongue. It was a reflexive response.
"It's well engraved."
He said so and stroked Vilma's lower abdomen.
She also lowered her head and looked at the spot where his hand was touching.
There was a small pink heart-shaped mark drawn there.
If you looked at it separately, it was just an insignificant tattoo. However, the pink color, the heart shape, and the location on her lower abdomen where her womb was located made this tattoo feel lewd.
"But still, just using it like this, the first stage is the limit. Hmm, as expected, if the effect is too good, the restrictions are severe."
"Wh, what is this…?"
Every time she looked at this tattoo, she felt a tingling sensation throughout her body.
"Ah, this? I named it the 'Yin Seal' magic. And this one in particular is the 'Seal of Submission'."
"Su, submission?"
"Don't worry. It's not like you'll die if I tell you to. It just makes you listen to me a little better."
It was a lie.
Of course, it wasn't to the extent of dying if he told her to, as he had said before, but it was still different from what he had implied. There were common effects shared by all Seals of Desire, and as the name "Seal of Submission" suggested, there were also special abilities. But he deliberately hid them.
Because it seemed more fun that way.
"Anyway, since I'm still inexperienced, you'll be very tired. Sleepy, right? You can sleep."

"Ah, yes, yes…"
As if she had been waiting for it, she closed her eyes and collapsed. He caught Vilma's waist, but even if she had hit the floor, she probably wouldn't have woken up.
He carried the deeply sleeping Vilma to the bed in the corner of the room and laid her down.
"Hmm, as expected, I need to mentally subdue her more to raise the stage. This is a restriction, so that's fine, but it also consumes too much of the caster's stamina and mana. I need to fix this."
After reviewing the magic, he sat on the edge of the bed and looked down at Vilma.
He brushed away the hair that was stuck to her lips with sweat. Her hair was mostly blonde, but it had a grayish tint towards the ends. It was a characteristic he had heard of many times, although he had never seen it in person.
Her face and description were definitely written in the documents Irena had given him. He had forgotten because her revenge ranking wasn't high, but seeing this hair brought back clear memories.
"To think I would meet someone of that bloodline. Is God really helping me with my revenge?"
Of course, that wasn't the case.
The only god that existed in this world was the Goddess, and she hated demons.
However, the Goddess, who couldn't deeply intervene in the world, only influenced the continent through indirect means such as oracles. It was also the Goddess who had given the oracle that made him the hero. Of course, she probably hadn't expected this outcome either.
"But it's still interesting."
An evil laugh, unlike his boyish appearance, echoed through the dungeon.
"But how are you going to infiltrate?"
"Huh?"
Irena, who had been patrolling the area around the dungeon and strengthening security, asked him.
"Didn't I tell you?"
"You only said you were going to infiltrate the Ulstro Kingdom."
"Ah, sorry."
He looked around and fell into thought for a moment.
He saw Irena and Vilma, who had woken up from her sleep.
Actually, he had planned to have Irena stay here and only act as a relay point with the Demon Lord's castle.
But he changed his mind. By chance, he had gained a good pawn named Vilma. She seemed suitable to be Irena's assistant. He thought it would be a great help in taking over the kingdom using the two of them.
He finished organizing his thoughts and opened his mouth.
"First, I'm going to infiltrate the royal palace."
"…Yes?"
"Ho, how?"
Both women looked surprised at his words about infiltrating the royal palace.
"It's simple. I'll use the martial arts tournament."
"I see. That could work."
"Eh? What's a martial arts tournament? …Uh… why are you looking at me like that? I, I might not know!"
Vilma felt embarrassed and ashamed by their gazes and shrieked.
"Seriously, a demon has to explain a martial arts tournament to a continent person."
"You probably just don't remember it well. You must have heard of it at least once. The Hero Commemoration Martial Arts Tournament."
"Uh…"
Even though she was told the official name, Vilma didn't look like she remembered anything in particular. Irena sighed softly and continued to explain about the martial arts tournament.
"In the war with the Demon Lord's army, the Ulstro Kingdom suffered the second greatest damage after the Ventorino Kingdom. Well, it's better than Ventorino, where the royal bloodline was cut off, but the hero, who was the only one from Ulstro among the hero's party, died, and the next heir to the throne also died. The people must have been struggling without anyone to rely on."
"That's where the current queen really started to shine. She led the surviving nobles and the people. But there was a shortage of talent. So she came up with a plan. Even though it had only been three months since the war ended, she held a large-scale martial arts tournament in honor of the hero."
"Many nobles were worried, but it was a great success. Ulstro became known as the land of knights, and the royal authority was solidified. After that, the martial arts tournament was held every three years, and this year happens to be the third year."
"Now that I hear it, I think I remember."
Vilma nodded.
Of course, she only knew it as a festival of the Ulstro Kingdom and didn't know there was such a background to it, but she didn't show it. She had already been unfairly labeled as stupid, and she didn't want to be treated like a fool any longer.
"That's a relief."
"Because my first human subordinate isn't a fool."
"…Th, then what next?!"
She didn't actually know how he was going to use the martial arts tournament, but she pretended to know and asked about the next plan.
"If a hybrid wins, it will attract too much attention and jealousy. I'll just get second place and become a follower."
"And then corrupt the members of the royal family. That's roughly the plan, right?"
"That's right."
Corruption.
Falling from the right path to the wrong path.
It used to be used in many different ways, but now it was only used in one way.
Betraying the continent and siding with the demons.
Whether it was for material reasons, seduction by a succubus, a magic-related contract, or being subdued by force and becoming a subordinate.
"Is that possible?"
Vilma couldn't help but say that without realizing it.
Corrupting the queen and the royal family of a kingdom? It sounded too absurd. What did they lack to side with the demons?
It was too serious to be a joke, and his handsome face wore a confident expression.
'Huh? Handsome? Wait…'
Suddenly, she remembered that the Ulstro Kingdom was ruled by a queen, and below her were only two princesses.
"Are you going to seduce them with your face?"
"Oh, close."
"Come on, even if that's the case, that's a bit…"
Vilma waved her hand dismissively.
Of course, the boy in front of her was handsome.
His appearance couldn't be completely hidden by his dark red hair mixed with demon blood. If she were a woman, she would glance at him at least once while walking down the street.
But he was just a boy who looked to be in his mid-teens. He wasn't handsome enough to make the queen and princesses sell out their country.
"I have this."
"…Huh?"
Suddenly, her heart started pounding.
Her face felt hot, and her stomach churned. Her eyes were drawn only to the boy's face.
Then she remembered the charm magic and the Yin Seal magic. She had forgotten about them because she had taken a refreshing nap and woken up.
"B, but isn't charm magic exclusive to succubi?"
Charm magic was a racial trait unique to succubi. Male succubi didn't exist. That's why only men had to be wary of charm magic. That's what had been known so far.
"That's right. This is just a similar magic that I analyzed and created. The conditions are strict, and the effect is weaker than the original. But it's useful, right?"
"…Yes."
"With the Yin Seal magic added to it, it's better than most succubi."
Perhaps he had withdrawn the charm magic, but she gradually returned to her normal state. However, her heart was still pounding.
'This person is a genius.'
Charm magic had never been deciphered by anyone before. This boy had done it.
Of course, there was an excuse for the human side. There were few succubi, and they were difficult to sample because they were demons, which were hostile creatures. On the other hand, the boy in front of her was a demon himself, so it would have been much easier for him to research.
But that didn't mean this achievement should be underestimated.
"By the way, I'm also good at other types of magic. White magic is my specialty, but I'm also proficient in black magic. I helped Irena with her ink magic. How about it, do you think you made the right decision by making a contract with me?"
He smiled brightly, noticing the change in Vilma's expression.
He was right.
She felt the worries she had until just now disappear completely. In the first place, she didn't have any patriotism or love for humanity. That's why she had made a contract with a demon to survive. Magic research and improvement of her skills. If she could achieve that with someone else's help, she was willing to sell her soul.
"Yes… sincerely."
"Haha, I like that you've become more proactive. Come to think of it, I haven't introduced myself yet. My name is Valdes. I'm the Demon Prince who will become the Demon King in two years."
Demon Prince.
A higher status than she had expected.
In the first place, the Demon King had died 18 years ago. Then his child would have ascended to the throne, or the position would have remained vacant. The boy in front of her was either the son or grandson of the deceased Demon King.
The highest or second highest position in the Demon Lord's army.
As a contract partner and superior, he was perfect.
"…Please take good care of me, Lord Valdes."
Hearing Vilma's response, Valdes raised his head and looked into the distance, obscured by the dungeon wall.
He thought of his former party members, those who had participated in the betrayal, and those who might have participated.
'Just wait a little longer.'
"I'll take everything from you."