Kaigaku arrived at Sensei Jigoro’s when he was just eight years old, dragging with him a monstrous ambition. From the very beginning, he declared—with a confident, arrogant voice—that he would be his successor, the next Thunder Hashira. No one contradicted him. Who would dare, in front of a boy with that much fire in his eyes?

Two whole years passed in brutal training—blood, sweat, sleepless nights, broken bones. Kaigaku began to master Thunder Breathing, slowly but persistently. He wasn't a prodigy… but his stubbornness made up for it. Every technique he shouted like the world needed to hear his power. Every strike was an attempt to make Jigoro proud.

And just when he thought he had everything under control, the visitors arrived.

Jigoro had mentioned an old friend would be stopping by. Nothing more. He never said that this man was the only Demon Slayer who had turned down the Hashira title, choosing instead to disappear into the mountains with a purpose: to train special slayers. Warriors from Taiyō no Hikari—a village hidden between cliffs, known for producing the best of the best. Practically a myth.

They were few. One or two per generation. But those bastards were strong, and adapted frighteningly fast. Rumor said they came from outside the country, their tan or golden-brown skin a sign of bloodline born under a fiercer sun.

Lies. Empty praise.

Kaigaku respected no one. But the moment he saw the old man Tadao, he froze. The man was Japanese, plain in appearance—except for his eyes. His gaze was a blade, a dry thunderclap before the storm. His voice wasn’t loud, but it shook the air.

He was meant to rest. But Tadao offered to give the boy a glimpse of his training. Curiosity, he said. Interest. Kaigaku accepted.

That was a mistake.

Tadao didn’t raise his voice. He didn’t shout techniques. He didn’t strike with fury. He simply brought him down—again and again. Quick, clean, as if sweeping away dust. In minutes, Kaigaku’s arrogance crumbled. By the end of the day, he had a split lip and a shattered pride. He didn’t cry—not in front of them. But the silence from his master was worse than any scolding.

Then, days later, Tadao returned. But this time, he wasn’t alone.

She walked behind him, saying nothing. She was young, maybe Kaigaku’s age. Her skin was golden, glowing under the sun. She moved with a kind of loud elegance, as if the ground belonged to her. Every step was sure, radiant, and filled with a sparkle so flashy, she didn’t need to speak. Her clothes were different. Her posture perfect. Her hair was tied up with beads that shimmered like lightning.

She said nothing. She didn’t mock him. She simply existed. And that was enough.

Kaigaku felt invisible.

From that day on, she trained near them. Not together—always separate. But every time he failed, he would see her nearby, watching. Never speaking. Never judging. Her presence alone gnawed at him. Her steps echoed like the rhythm of something he would never reach.

He tried to ignore her. Trained harder, screamed louder, filled the air with rage. But his style was noisy and violent. Hers was elegant, almost beautiful. Like the fight was a performance.

And then… he began to hate her.

"Stay away from me!" he growled every time she tried to help him up. "You think you’re better just because you’re a little more important?! You’ll see when I surpass you —you’ll be nothing compared to me!"

But she never responded. She just looked at him. Calm. Radiant. Unshaken.

Kaigaku started training at night. Tearing his muscles apart, desperate to catch up to something he didn’t understand. He no longer wanted Jigoro’s pride or the Hashira title. He just wanted to erase that blinding shadow that followed him without a sound.

But the more he hated her… the emptier he felt inside.

That day's training ended, just a congratulations from Jigoro, nothing more, you... you were damn cool doing push-ups. The worst part? You weren't even training, it was just damn visits!

"You shouldn't be here..." The young black-haired man spat out his words. "You're a damn nuisance!!!"