A fifteen years old Sona watched from a distance as her queen lost another sparing session. She had lost count of it, but probably it was their fiftieth or sixtieth sparing session, of which none won by Tsubaki. Though, it was not a surprise. It would be a surprise if Naruto miraculously lost against her queen. Her knight was admirably strong, stronger than even her dear big sister. Sona envied him for his strength and tactical battle, but at the same time she admired him for that reason as well—along with his kindness and his workaholic ethic.
Ever since he learnt that he had become a devil, never once had Naruto cursed her for reincarnating him without his permission. Even though he was not happy that he was no longer human, he nonetheless thanked her for saving his life. At that time Naruto murmured that he still had the chance to return, but he refused to talk about it when she asked what did he meant by that.
Surely it had something to do with complex magic that her knight studied like his life depended on it: [Rune Magic] and [Space-Time Magic].
Talking about magic, her knight had learnt most magic that existed in Sitri's Library. She didn't know how he managed to accomplish the feats that even a devil as old as her father could not. Though, he only dedicated himself to elemental magic and [Teleportation Magic]. He had even brought that magic to an unimaginable level. [Teleportation Magic] was used to move from one place to another, shortening the time it took to a mere second. Yet, Naruto's use of [Teleportation Magic] was mainly for combat. It was not an exaggeration when Ajuka Beelzebub claimed him to be the fastest devil inside his magical territory.
And thanks to him for helping her in both magic and combat, Sona had mastered her [Water Magic] to the level that she could create an army of giant sea-serpents with ease. Even though she hadn't yet reached the level of her sister, it was admirably enough that a devil as young as her had reached such level of strength. In two or three years, if she kept on training as hard as her knight, surely she would be able to stand equal to her sister—or so she wanted to believe.
"Sona, something on your mind?"
Sona's train of thought abruptly came to a halt as her knight's voice invaded her ears. He was walking alongside a defeated Tsubaki toward her, who was sitting on a chair outside the sparing arena. Naruto had grown taller over the years, so was his blond hair. His whiskers, which Sona assumed as birthmark, became thinner for no reason—so thin that one had to look closely to see it.
"Nothing to concern about," she said. "By the way, tomorrow Tsubaki and I will start going to high school in human world. Are you sure you don't want to join us?"
"I will stay in underworld for a year or two. I'll join you by then. I still need to learn more about magic from Lord Ajuka. It is essential for me to master certain magic."
"Why are you so obsess with [Rune Magic] and [Space-Time Magic]?" Sona finally asked the damn question, probably for the dozens of times since he started learning those magic.
"I want to know whether this universe indeed has boundaries or not. If it has boundaries, what exists beyond it? If it has no such boundaries, then how large our universe truly is? Since Trihexa is sealed at the end of the world, what exists beyond it? There are so many questions to answer."
Sona's thin lips curled upward. That was the first time Naruto gave her answer which was not "because those are interesting". And her smile grew bigger as she came to connect the dot behind the purpose of this blond knight of hers. "Do you plan to go to another universe, assuming there's such universe?"
Naruto didn't confirm nor denied it, he just said there's a possibility her question to be true. Though, whether that possibility remained a possibility was the story for another time. But then again, her way of meeting Naruto was not normal at all. Could it be that he wasn't human of their world?
"I see," said Sona with understanding. "I'll help you as much as I can."
"You have helped me enough," responded Naruto with a gentle smile. "You should focus on your goal. Even though the satans support you, creating such a school will surely get oppressed by the old-geezers that govern the entire devil territory. It is like you are insulting the way of the devil. You have to make them to support you one by one."
Sona smiled. There's no need to further the argument with the blond—he was hell-bent on excluding her from his goal. And it's fine. Sona didn't need Naruto's permission to help him. Even though she couldn't offer much help regarding [Time-Space Magic] (her aptitude was not good enough to learn that magic), she had secretly studied [Rune Magic]. More than that, Sona didn't forget how she accidentally summoned the blond through her failure of activating the spell properly. Perhaps it would give her insight to figuring out the truth regarding the blond's origin—assuming that he was indeed a human of another universe.
"Alright." Sona nodded her head. "Tsubaki and I will prepare for our departure. We will leave Underworld tonight along with Rias, Akeno, and Koneko. Will you return to see our leave?"
"Of course, there's no way I'll miss it. I will bring Serafall along. She's still whining about you leaving her side. She hasn't return home for two days straight, probably thinking that you'll change your mind and persuade her to go home and live together just like before."
Sona knew that. Her sister wasn't happy with her decision to study in the human world. It wasn't because her sister didn't support her goal. Like Naruto and both her parents, her sister supported her goal to the fullest. However, she didn't like it that she couldn't stay by her side and pampered her to her heart content. Sona of course happy that her sister loved her so much, but she didn't want to hear her saying that she would be the one to marry her. That's so unhealthy.
"Very well, I expect to see you and my sister tonight. Let us go, Tsubaki."
Naruto nodded his head and watched as Sona and Tsubaki left the training arena. Sona's strength had reached those of Ultimate-Class Devil (at least the weaker ones), while Tsubaki would soon become as strong as High-Class Devil. With those strengths, they surely could handle themselves just fine ‒ Serafall didn't need to worry about their safety at all.
" I prefer the loud-mouthed stupid you."
The train of his thought came to a halt as the deep voice of the mighty fox resounded in his head.
It was amusing how the mighty kyuubi became a salty guy. But Naruto understood his only company in this foreign world. It was similar to him. If Kurama was prisoned inside him, Naruto was caged by the so called evil piece. He lost his humanity, and he's nothing but a slave to Sona. Even though Sona didn't think it that way, that was the harsh truth—the common opinion among the nobility of devil. Even though he took the offer of promotion, it wouldn't change the fact that he's still a slave.
"People change, Kurama. Pain changes them. Having experienced near-death situation, finding myself no longer human, stranded in a world where there is no real chakra… It is a miracle if I don't change. If I was my old self, I would never have reached this far ‒ we might never be able to return. Is that what you want?"
" This world is not bad. If I managed to take over your body, I'd have become the strongest in no time. There are youkai in this world, I can easily become their supreme king. Khahahaha."
Naruto shared the laugh. Ever since he dreamt of the life of Asura, the supposed to be his predecessor, he had become closer to the nine-tails. Of course Kurama tried to suggest him to over him his body every now and then. But nonetheless, it was nice, something he appreciated very much—the existence of Kurama was the only thing in this world which reminded him that the world he's living in was not his.
"As much as I want to indulge you in your delusion, I think I should hurry to meet Ajuka. He has been helpful for my cause. I feel bad for not arriving on time. In a way, he is my teacher."
" The old you would never do such thing. You pretend to learn magic from him, but in truth you are searching the secret of evil piece in his workplace. You have truly fallen, haven't you?"
"I don't think so. In fact, I have become a better shinobi."
" Hmph, whatever. I want to sleep. Don't bother me."
It was funny to hear that from the fox. In the first place, he was the one who started the conversation—Naruto should be the one to say that to the fox. Nevertheless, Naruto just shook his head and teleported himself out of the training ground. He appeared right on top of the massive building of Sitri Mansion, before creating a small magic circle which would teleport him right to the front door of the devil genius' workplace.
A few knocks on the door, a female devil wearing maid uniform opened the said door for him. "Lord Ajuka has been waiting for you, Lord Naruto," she said, motioning the blond to have access inside the workplace. And in he went.
—Two Years Later—
Naruto had come to the final conclusion: In order to cross the border of the universe, he had no choice but to go to the Dimensional Gap. Otherwise, nothing could be done to create path to another universe. It didn't matter how excelled had he become at both [Space-Time Magic] and [Rune Magic]; it simply didn't work. Like Ajuka suggested a few weeks ago: "Creating the portal at the center of the Dimensional Gap is probably the only way to travel to another world—assuming there's indeed another world as we think."
It was a simple solution, which both he himself and Ajuka agreed at. However, the problem was the existence of The True Dragon God who roamed over the void. That beast was overwhelmingly strong. Naruto indeed had not seen it yet, but he trusted the green haired devil on his words. In his base form, Naruto believed he could handle Ajuka's Kankara Formula—he'd need a certain sword from the vault of Gate of Babylon, though. If he used Kurama Cloak Mode, he believed handling both Sirzech and Ajuka at the same time wouldn't be a problem.
However, such strength was not enough to defeat the True Dragon God. There's an option to seal it, but the problem was there's no place to seal that dragon. And Great Red was too strong to be sealed inside human, yet alone a mere weapon. Though, he could seal it inside himself. But… Naruto didn't want to do that. It was too dangerous. The dragon was the ruler of dream; it would pose a problem if he came to sleep while the dragon was sealed inside him. It might be able to take over.
There's an option with EA, but the sword was too dangerous to use ‒ Dimensional Gap might collapsed just by him unleashing the strongest weapon that existed inside the King of Heroes' treasury. If the gap collapsed, so would the world. For that sole reason, he might never choose to bring out the sword, unless it was the ultimate last choice.
There's an alternative case to use EA in a safe way: He needed to prison himself and Great Red in a strong dimension. EA then would be unleashed upon Great Red along with the dimension, thus enabled him to prevent the destruction of Dimensional Gap. However, creating a dimension strong enough to contain Great Red long enough to defeat him was no easy feat. With his current strength, it hadn't become an option yet. Also, there's no certainty that EA could destroy Great Red completely. Therefore, it was better to avoid anything risky.
Naruto hadn't managed to synchronize Asura's Chakra with his, therefore it was impossible for him to use Asura's Six Paths Senjutsu. According to Kurama, he needed to understand senjutsu to tap into Asura's Chakra. In his world, there're ways to learn senjutsu. However, in this world only nekushou could utilize senjutsu. At least, that's what known about the rarest power existed in this world. And there're only two nekushou in this world: Sona's rival's rook and her sister—and only her sister who's known to be capable of utilizing senjutsu.
"Naru-tan! Naru-tan! I'm ready! Let us meet So-tan!"
Naruto's thought came to a halt as that voice screamed its way inside his ears, forcing him to shift his head toward the source.
Serafall in her wholesome magical girl outfit along with magical staff in her hand and a magical hat on her head was already standing a few feet from him with a beaming smile on her face.
Naruto smiled. "I don't mind accompanying you anywhere even with that outfit," he said. "But I think you'll embarrass the hell out of Sona. The worst case, she may refuse to meet us."
"What?! No way! So-tan will never refuse to meet her beloved big dear awesome sister! She is missing me very much, she'd jump into my loving embrace as soon as we arrive!"
"Then, how about making a bet? Should she jump into your loving embrace, I will join you on your magical girl show. However, should she feel embarrassed, you will accompany me sight-seeing the beauty of Kyoto. How is it?"
"My, Naru-tan! Are you asking this awesome magical girl to a beautiful date? How bold of you! However, I have to stress it that my heart belong solely to So-tan! You can hold my beautiful hand, but my first kiss goes to So-tan, okay?"
"Having a date with you would be nice, but unfortunately, Serafall, that is not my intention. You see, I'm interested to know whether or not it is true that no other youkai can utilize senjutsu except nekushou. As far as I remember, you are the one in charge of Foreign Affairs. Am I wrong?"
Serafall became a bit serious, just a little bit. "Now that I remember you have similar energy to youkai. Are you perhaps planning to learn senjutsu, Naru-tan?"
"I think it'll be useful to me," admitted Naruto.
"No. You'll not be learning it. Not as long I'm alive." That time, Serafall's playfulness had disappeared without trace.
"I think I don't need to ask your permission, am I wrong?"
"Learning senjutsu is dangerous, Naru-tan. It can cost you your sanity. I don't want to see you get hurt, and I absolutely hate it when So-tan feels sad by seeing you getting hurt. Besides, you are already strong, Naru-tan! Ajuka-chan confirmed that you are strong enough to stand equal to him even when he's using his Kankara Formula. You're easily the third strongest devil in the entire underworld."
Naruto let a little smile appeared on his lips. He understood Serafall's reason. But it wouldn't stop him from learning it.
"Very well, I'll not learn it." Naruto lied. "But, knowing it will not be a problem, right? Are you against it as well?"
"Well, knowing it certainly will not be a problem. Very well, this awesome magical girl shall fulfill your desire of dating her—the most beautiful magical girl to ever exist—should she lose the bet!"
"I do not exactly want to date you, but whatever. So, are we leaving now?"
"Of course! The sooner we meet So-tan, the better for me!"
That said, the two left the underworld immediately. The magical circle brought them just on top of the school's rooftop. Naruto had visited the school twice, so he could teleport to the place without any preparation.