As we passed through the covered walkway, I looked out over the training grounds where children were intently thrusting their arms forward, trying their best to manifest magic bullets and spell circles during a practical magic lesson. Our next destination was the gymnasium.
Inside, the voices of energetic children echoed all around.
And standing before them, instructing with passion, was none other than Sairaorg.
"Listen up! A proper punch starts with a firm stance, keeping your elbows tight and thrusting your fist straight forward!"
"Yes, sir!!"
He was currently teaching the basics of martial arts—specifically, the straight punch.
If not for the setting being a school gym, the scene could have been mistaken for a karate dojo.
Noticing us at last, Sairaorg called out with his booming voice.
"Look, everyone! The Oppai Dragon team has come to visit!"
"Wow! It's the Oppai Dragon!"
"Switch Princess is here too! And so is Darkness Knight Fang!"
At his words, the children rushed over in excitement to see their favorite stars from the Underworld.
...Me? Well, some of them gave me confused looks. Can't blame them. My character, All Evil, is usually shirtless, with magically painted tanned skin, a bandana, and a body covered in suspicious-looking runes.
Meanwhile, here I am with no headgear, my natural pale Japanese complexion, and a winter school uniform. It's no wonder the kids didn't recognize me. It stings a bit, but maybe it's for the best. If they did realize who I was, I'd probably be bombarded with "Die, All Evil!" chants or something. Yeah… better to stay under the radar.
While Issei and Yuuto entertained the kids on stage with an impromptu performance to burn off their excitement, Sairaorg approached us.
"A place of learning truly is a wonderful thing," he said. "In the Underworld, there are schools, but they're mostly for nobles and the elite. With that comes the burden of status, power struggles, and hidden agendas. But here, the children gather with a pure drive—to chase their dreams and form friendships. That's beautiful."
President Sona nodded softly in agreement.
"Japan is a good country. Everyone has the right to learn. Many of the children gathered here were unable to attend normal schools—whether because they lacked status despite having talent, or had status but no magical ability. Among devils, especially, there's a strong emphasis on magical prowess. It's not uncommon for students to be rejected simply because they lack it, regardless of their other strengths."
"Which is exactly why this academy was built," Sairaorg continued. "To give all children, regardless of background, a chance to grow and realize their potential. My mother once told me: 'Even if you lack magical power, it's fine. Excel in something else—whether it's strength, intelligence, or anything that can be honed. If it leads to great power in the end, that's what matters.'
"I've taken the role of strength. Every child here throws their punches with all they've got. Once, my fists were only good for breaking things. Now, with these same fists, I can teach. I can inspire. That… makes me unbelievably happy."
Hearing this, Rias-senpai chuckled.
"Fufu, Sona and Sairaorg, you both have the look of teachers now."
"Hmm? Is that so? —Well, I've still got a long way to go. I'm just mimicking what I read in education books for now."
"There's a first time for everything. For us, for this academy… even for the children. We're all just beginning. So let's grow together."
As the three next-generation leaders of the Underworld envisioned a brighter future, the show on stage reached its climax. Darkness Knight Fang slashed, sending the Oppai Dragon flying.
"Oppai Dragon, hang in there!"
"Yeah! Now's the time to call Switch Princess, everyone!"
"R-Right! —Switch Princess!"
"Switch~!"
The kids' cries for the Switch Princess grew louder and louder.
Funny… this was supposed to be just a quick spar between Issei and Yuuto.
"Looks like they're calling you, Rias," I said.
"Yes, we can't disappoint them. Time for the Switch Princess to make her entrance!"
"Hmph, I know, I know!"
With a slight sigh, Rias-senpai activated a small communication magic circle and gave Issei the signal.
From the stage, he shouted dramatically:
"Summon! Oppaaaaaai!!"
And with that cue, Rias teleported onto the stage in a flash of magic, stepping into her role.
========
After the impromptu hero show wrapped up, we parted ways with Sairaorg and made our way to a building a short distance behind the main school.
At Kuoh Academy, our Occult Research Club was housed in the old school building. But this was a brand-new academy—there was no old building.
Instead, there were places resembling traditional Japanese dojos and athletic courses with obstacle-like elements, including ones where falling would plunge you into a pool of water. It was quite the setup.
What's more, this area seemed to have gathered the largest number of children and parents we'd seen all day.
Approaching one of the dojos, we spotted an elderly man in black training garb moving gracefully.
Upon seeing him, Rias-senpai reacted... explosively.
"Wha—!? T-That's unmistakably... a ninja!!"
She was so shocked she could barely form words. Sona's glasses glinted ominously as she smirked.
Sure enough, the man on stage was dressed like a traditional Japanese ninja.
"That's right," said Sona. "This is the man responsible for even neutral noble families siding with our cause for the Underworld's schools… In other words: NINJA."
At those words, Rias spun toward me and grabbed my shoulders, shaking me violently.
"IKKI! You knew a ninja and didn't tell me!?"
Ow ow ow! You're going to shatter my collarbones! Rias is insanely athletic, even if the story never emphasizes it.
"Wait, I didn't know him personally! And you were there, too, remember? Back when Loki attacked?"
That seemed to jog her memory.
"Ah! Salamander Tomita!"
"Exactly. He mentioned that he became the disciple of a ninja and learned Kappa-style ninjutsu. So we figured that if Azazel traced Vali's contacts, we might be able to reach his master."
"Right… that was before D×D was officially formed, so we had him introduced to us discreetly. He's from a prestigious ninja lineage that still preserves real ninjutsu to this day."
Issei, raised in modern Japan, looked visibly skeptical.
Can't blame him. "Real ninjas in the present day" is hard to swallow.
Meanwhile, Rias was sulking. "Ugh! I can't believe I missed this!"
"But still," Issei said, "it's surprising that a ninja would agree to teach at a devil school."
"He's from the Iga clan," Sona replied. "They were open to it—provided the right conditions."
"The IGA clan! A ninja style that values contracts and compensation! Perfect match for devils!"
Rias-senpai was clearly losing her composure.
"Sona! If we ask, can we take his class too!?"
"No fair, Xenovia already got ahead of us! I want to learn ninjutsu too—it would help strengthen Heaven's forces and benefit Lord Michael!"
Now the Holy Sword duo were cornering Sona in excitement. Is Xenovia planning to use ninjutsu to cover her lack of technique?
"Should we explore combining ninjutsu with magic?" Akeno pondered.
"I wonder if there are any forbidden techniques," murmured Ravel, intrigued.
Everyone was seriously considering how to incorporate ninjutsu into their fighting styles.
But for now, we decided to stay quiet and listen to the instructor's lecture. The ninja's name, apparently, was Tanmon Momochi. Rias and the others pulled out notebooks without hesitation. In fact, most of the adults around us were either scribbling notes or filming.
They clearly intended to replay this lecture until their devices wore out.
"Many believe that ninjas use their trained bodies to infiltrate enemy territory and defeat foes. While that's not wrong, it's not entirely right either. Allow me to show you what I mean."
He unwrapped a cloth bundle, revealing tools like kunai, shuriken, a straight ninja sword, smoke bombs, and claws. Both kids and adults leaned in, wide-eyed.
"Ninjas must infiltrate, escape, and fight—all alone if necessary. That's why intelligence gathering is vital. Based on that, we choose the tools needed for each mission. But packing light comes with risks. So ninjas used their ingenuity."
He picked up the ninja sword.
"This is straight-edged, unlike a katana. That's because indoor fights in tight spaces require thrusts, not swings. See this hole in the scabbard's base? It acts like a snorkel for underwater stealth movement. And this long cord? It allows retrieval after using the sword as a foothold to climb walls.
"One tool, many functions. That's what makes ninjutsu special. Countless predecessors refined this blade over generations.
"Which is why I say: ninjas weren't just tool users. They were scholars, strategists, creators—innovators in the shadows."
"Woooow!!"
The crowd erupted in admiration. The kids sparkled with wonder.
"This academy encourages the learning of diverse skills and knowledge. So I'll share the knowledge of ninjas. But don't simply imitate. Think. How can you use your magic and power to enhance and evolve these techniques?
"Expand your perspective. Embrace new values. And above all… enjoy it. That is the first step to mastering the ninja arts."
As Tanmon Momochi finished, the audience burst into thunderous applause.
"Amazing! I heard the rumors, but never thought the legendary ninja himself would be teaching!"
"Indeed, Satan Red. Knowing they were researchers too makes them feel closer to us."
"Satan Blue, you've always liked inventing things! I'm thinking of making a ninja my next servant."
"Sounds fun to me!"
"Too bad Satan Green already filled their roster. I envy Satan Pink for still having room for new servants."
"Oh come on, Sairaorg—I mean, Satan Red—you already have SAMURAI Okita Souji!"
"Hahaha! So I do!"
...Yeah. Let's all pretend we didn't just see the full team of mystery Sentai-like Satans. Issei, stop staring. Oh—look, Grayfia appeared (probably in disguise as Satan Yellow) and is now magically restraining and dragging them all off.
...She must've had a hard time sneaking out of the Gremory castle.
It would still be a little while before a certain ninja—not unlike a certain non-stealthy shinobi from a certain anime—would rise to prominence in the Rating Games of the Underworld.
But angels and fallen angels, having taken serious interest (and a bit of panic), would soon sneak into the academy to take these classes themselves.
And so, Angel Ninjas and Fallen Angel Ninjas were born—rapidly accelerating the growth of ninja techniques through competition.
Perhaps… it wouldn't be long before ninjas secretly ruled the world.