Five days later, inside the training hall of the Butterfly Mansion.
Sunlight streamed through the skylight, casting a warm golden glow across the polished floor. The peaceful setting clashed sharply with the tension thick in the air.
Clang, clang.
At the center of the hall, Raiden and Shinobu Kocho moved in blinding bursts of motion. Their Nichirin blades collided in rapid succession, sparks scattering like fireflies.
Raiden's blade crackled with golden arcs of electricity. Each swing carried a low rumble, and his speed was so extreme that the path of his sword was nearly impossible to follow.
Opposite him, Shinobu wielded her slender pink Nichirin blade with effortless grace. Her movements were light and precise, as if she were gliding rather than stepping. Though she lacked overwhelming physical strength, her refined footwork made her impossible to pin down.
Steel rang again as their blades met midair, stirring sharp gusts of wind across the hall.
Raiden missed a strike, then instantly shifted his rhythm. Lightning surged along the edge of his blade as he pressed forward.
Shinobu's steps retreated half a pace, controlled and deliberate. In the same breath, she thrust toward his chin with surgical accuracy.
Raiden's violet eyes narrowed, and a faint, knowing smile curved his lips.
Not good.
Shinobu's instincts flared the moment she saw that expression.
During their recovery period, Kanao had been responsible for Tanjiro, Zenitsu, and Inosuke's rehabilitation training. Shinobu had personally taken charge of Raiden.
On the first day, she had been genuinely startled.
When she previously watched Raiden spar with Sanemi Shinazugawa, she simply thought he was talented, capable of enduring under the Wind Hashira's pressure. But once she faced him herself, she realized she had underestimated him.
His speed, strength, and mastery of breathing techniques had all improved dramatically.
If she had not possessed the experience and composure of a Hashira, she might have found herself at a disadvantage on the very first day.
Now, after several days of exchanging blows, she recognized the intent behind his gaze.
Her thrust shifted mid motion, turning into a horizontal slash aimed at his shoulder.
Raiden blocked smoothly. In the next instant, the golden lightning along his blade faded into a deep, fluid blue.
Water Breathing, First Form.
His swordplay became seamless and flowing, one strike blending into the next without interruption.
Shinobu withdrew immediately, her eyes narrowing slightly.
Again. Water Breathing.
How had Raiden learned it?
His raw power was not yet equal to hers, but he was far more troublesome than most demons she had faced. His speed was erratic, his transitions between Breathing Forms unpredictable. Every exchange demanded her full attention.
Raiden felt a flicker of disappointment when she disengaged.
If she had reacted a fraction slower, he could have disarmed her.
A Demon Slayer without a Nichirin blade was significantly weakened. From there, wearing down the Insect Hashira would only be a matter of time.
Still, if defeating her were that easy, she would not be a Hashira.
Their shadows stretched across the wooden floor. A heartbeat later, they clashed again, light and steel intertwining in rapid succession.
Each collision echoed through the hall.
Watching from the side, Tanjiro swallowed.
"Raiden is that strong? He can fight Miss Shinobu evenly?"
He now understood what the title of Hashira meant. Shinobu was one of the strongest swordsmen in the entire Demon Slayer Corps.
Zenitsu stared wide eyed.
"Raiden got stronger again. Is that awakening really that amazing?"
He could barely track the movements. Shinobu's silhouette appeared in flashes, but when Raiden accelerated, all he could see were streaks of golden light cutting through the air.
"That idiot Raideku. Fight me! I want a duel!"
Inosuke's boar mask puffed out a stream of heated breath.
For the first two days after the battle at Mount Natagumo, he had been unusually quiet. Failing to defeat the Spider Demon Father had bruised his pride deeply.
That gloom vanished on the third day, when Raiden visited him.
Without warning, Raiden shattered a training gourd larger than Inosuke's torso in a single strike.
Then he stepped closer, casually resting a hand on the top of Inosuke's mask.
"If you are weak, train harder."
That was all he said.
Inosuke had exploded in outrage. He might not read well, and he might miss subtle meanings, but that message was clear enough.
Since then, he had trained harder than anyone, shouting daily that he would twist Raiden's head off.
Back in the hall, the sparring finally reached its peak.
Shinobu vanished from sight, reappearing in a flash as she executed Insect Breathing, Dance of the Hornet, True Flutter.
Her blade darted forward with lethal precision.
Raiden halted, lowering his sword as the exchange concluded.
Shinobu sheathed her blade gracefully.
"Not bad. Your control over switching between two Breathing Forms is much smoother now. If you learn another one, even I would find you much harder to handle."
Her smile was bright, and this time entirely sincere.
Raiden inclined his head slightly. "You give me too much credit."
He had limited himself to Thunder and Water Breathing. Revealing everything at once would not only expose his talent, it would risk drawing Muzan Kibutsuji's direct attention.
He was strong, but not strong enough for that.
He studied her expression, then tilted his head slightly, voice light.
"You seem to be in a better mood today, Miss Shinobu. Did something ease your heart?"
She paused.
Was it that obvious?
After speaking with Tanjiro the previous night, the weight she had carried for so long had lessened. Her smile no longer felt like a mask.
"It is a little better," she admitted softly.
This time, her smile carried genuine warmth.
Raiden met her gaze steadily. His tone shifted, casual but direct.
"Then, Miss Shinobu, would you be willing to be friends?"
For a brief moment, she looked surprised.
Then she smiled, gentle and unguarded.
"Of course."