Early morning at the Butterfly Mansion, wisteria petals drifted lazily through the courtyard.
After watching the Hashira demonstrate their powers the day before, Erika had made up her mind; she wanted to learn Love Breathing from the Love Hashira, Kanroji Mitsuri. She thought it would help her control her ribbons better, so she immediately began her training with Mitsuri right after breakfast.
Meanwhile, Akira had gone off to read old handwritten documents for his research on demons.
"All right, Erika-chan!" Mitsuri said with her usual radiant smile, clapping her hands together. "Ready to make your muscles fall in love with pain?"
Erika blinked. "I'm ready… Wait, what did you just say?"
But Mitsuri had already begun, smiling radiantly.
Erika's training began with the basics: stretching, running, and lifting boulders. To anyone else, it would have been sheer torture, but to Erika, who is a genuine superhuman, it was easy.
Mitsuri had planned to spend several days building Erika's flexibility, endurance, and stamina before moving on to the next stage. But to her surprise, Erika completed each exercise with ease.
"Wow, Erika-chan! You're incredibly flexible!" Mitsuri gasped in delight.
"Well, I'm part vampire," Erika admitted, wiping a bit of sweat from her forehead. "And I've trained a lot, so I'm good at this."
It was true. The original Erika wasn't much of a fighter, but this one had trained in martial arts for years, so she wouldn't be a burden to Akira. She was, by all means, surprisingly athletic.
Mitsuri tilted her head, tapping her chin. "Hmm… what should I do now? You see, I wanted to keep you training like this for a few days, and then the next step would be leaving you alone in a mountain full of deadly traps to test your instincts, but I haven't prepared any of that yet. What should I doooo…"
After a long moment of dramatic thinking, her eyes lit up. "Hmm… well, maybe we can start Love Breathing already!"
"Already?" Erika asked, a little surprised.
"Mm-hmm!" Mitsuri beamed. "All that running and stretching was to make your body flexible and strong! But Love Breathing isn't about muscles or stamina," She pressed a hand dramatically to her chest. "It's about the heart!"
Erika blinked. "Heart?"
"Yes!" Mitsuri's eyes sparkled. "Love Breathing channels the warmth in your heart, the love you feel for people, for life, for everything! You let that warmth spread through your whole body, and it makes your movements faster, lighter, and prettier!"
Erika stared, utterly confused. "So… it's emotion-based breathing?"
"Exactly!" Mitsuri spun gracefully, her whip-like sword flashing as sunlight danced across the blade. "It's not about raw power, it's about turning your feelings into strength!"
"So… love improves physical performance?" Erika asked dryly.
"Love improves everything!" Mitsuri declared proudly, eyes sparkling with sincerity.
Erika sighed. "How did I end up learning to fight with the power of love?" she thought, already suspecting Akira could probably explain the science behind it. But since last night's… "incident," she was still too embarrassed to talk to him.
"Okay, Erika-chan!" Mitsuri said brightly. "Watch closely, all right? I'll show you first!"
Erika nodded as Mitsuri began her demonstration.
She took a deep breath, her movements flowing like silk in the wind. "Love Breathing: First Form — Shivers of First Love!"
She dashed forward, her whip-like sword curving beautifully through the air, slicing through a wooden target in one elegant motion. The blade cut cleanly through a wooden target, striking multiple points at once. Each swing was filled with grace, precision, and warmth, like a dance rather than combat.
When she stopped, the air still rippled faintly with motion. The target fell apart into cleanly cut pieces.
"That's Love Breathing!" Mitsuri smiled. "See? When you move with your heart, your body just… follows!"
Erika blinked, genuinely impressed. Mitsuri's control over such a difficult weapon was stunning. "That's… amazing."
"Okay, Erika-chan, now it's your turn!" Mitsuri encouraged.
Erika nodded, the red ribbons tied to her arms twitching faintly as if responding to her will. "I'll try."
She inhaled deeply, slow, steady, and calm, trying to match Mitsuri's breathing rhythm. Then, she swung her arms.
The ribbons sliced through the air… but lacked Mitsuri's fluidity or grace. The strike hit the wooden target, but only left a shallow mark.
The target was only nicked.
Erika exhaled sharply in disappointment. "That was terrible…"
"Good start, Erika-chan!" Mitsuri said brightly. "But you're a little stiff! When you move, move with love!"
Erika deadpanned. "But I don't know how to do that."
Mitsuri placed a finger to her chin, thinking. Then her face lit up again. "Feel something that makes your heart flutter! Maybe something or someone you love! Make that feeling flow through you as you move!"
Erika froze for a moment. "…Someone?"
"Yup!" Mitsuri said cheerfully. "Think about them! The way they make you smile, or how you want to protect them! Then breathe that feeling into your swing!"
Erika hesitated, then sighed softly. "Alright…"
She focused again, this time thinking of a certain someone's stupid face glaring right at her from the wooden target, and struck.
But instead of slicing the target… her ribbons wrapped around it and hurled it towards the mountains in the distance.
Both Erika and Mitsuri stared in silence.
"Uh… what does that mean?" Erika asked hesitantly.
"I… don't know either," Mitsuri admitted, equally confused.
They continued training until nightfall. Though Erika's control over her ribbons improved, she still couldn't replicate Mitsuri's Love Breathing. It wasn't a failure, but it felt like the style simply didn't resonate with her.
For some reason, Erika felt deep down that Love Breathing wasn't meant for her.
After her training with Mitsuri, Erika decided she needed to talk to Akira about their next steps.
By the time she returned to the Butterfly Mansion, the sun had long set, and the grounds were bathed in the soft glow of moonlight.
As she walked along the wooden veranda, she stopped.
There stood outside a girl under the wisteria trees, beautiful and motionless, bathed in pale moonlight. A single butterfly rested on her open palm, its wings glowing faint blue.
Erika hesitated, unsure whether she should speak. After a moment of thought, she decided it would be rude not to.
"Ah, hai," she greeted softly. "Are you a Demon Slayer too?"
The girl blinked slowly, meeting Erika's gaze. Then, with a small, polite smile, she nodded and yet said nothing.
The butterfly fluttered its wings once but remained perched on her hand.
Erika waited. And waited.
But the girl didn't speak.
"She's… very quiet", Erika thought. "Or maybe she just doesn't want to talk to strangers".
Before the silence could become unbearable, a familiar voice called from down the hallway.
"Oh! Erika-san! You're back! Did you finish your training?"
It was Aoi, carrying a tray with folded towels.
Erika turned toward her and smiled politely. "Good evening, Aoi-san."
Aoi approached, smiling back, but there was a hint of awkwardness in her expression. The two stood there for a few seconds, neither of them quite sure how to begin the conversation.
Erika knew why.
Aoi had seen that last night, when Erika drank Akira's blood. Even if she hadn't realized what was actually happening, the position they were in had been… compromising, to say the least.
Wanting to change the subject, Erika quickly asked, "Um… do you know where Akira is?"
Aoi's expression shifted oddly, as if unsure how to explain. "Well… about that."
She paused, then sighed. "First, he trained a little with Tanjiro and Inosuke this morning. Then he locked himself in the reading room for half the day. After that, he came to me asking for… cotton seeds."
"Cotton seeds?" Erika repeated, frowning. "Why would he need those?"
"I… don't know either," Aoi admitted. "He took them and went into the forest for a while. Then he came back, borrowed the kitchen, and… made something big."
Erika tilted her head. "Something big? What did he make?"
"I don't know," Aoi said helplessly. "But it was definitely big. And then he ate some food and went to his room. He hasn't come out since."
Erika exhaled slowly, rubbing her temple. "What the hell is he thinking now…? Don't tell me he made another bioweapon or something."
"...Another?" Aoi asked, looking slightly alarmed.
"Never mind," Erika said quickly.
There was a small silence before Aoi spoke again. "Would you like some dinner, Erika-san? I can prepare something for you."
Erika shook her head. "No, thank you. I already ate at Mitsuri-san's place."
"I see. Then, have a good night."
"You too," Erika said with a small smile, bowing slightly before heading toward her room.
The corridor was quiet, the faint hum of cicadas echoing outside.
But when she reached her door and slid it open.
And she froze.
Her eyes widened.
Her breath caught in her throat.
Because what greeted her inside…
was something completely unexpected.