Demon Slayer: The Ultimate Defense System

"Yohan!"

"Looks like you don't need any treatment after all."

No sooner had Yohan and Tamayo stepped into the Butterfly Mansion than Shinobu Kocho and Mitsuri Kanroji popped up out of nowhere. Clearly, they'd been waiting for them.

Yohan reached out and gently ruffled Mitsuri's hair, then glanced at Shinobu, who stood with her arms crossed and a curious glint in her eye.

"You want one too?"

"Of course not!" Shinobu snapped, face flushing as she hurriedly denied it.

Without waiting for a reply, she grabbed Tamayo's hand. "Tamayo, I've got a new experimental medicine in my room. Come have a look."

Tamayo had no choice but to let herself be dragged off, only turning back to give Yohan a wry smile before disappearing with Shinobu.

By evening, Kanae Kocho returned.

"Well, well... you all decided to eat without me, huh?" Kanae dragged her tired body step by step toward the dinner table.

Even after Yohan left, the meeting on the other side had gone on for quite a while. Most of it had been Kagaya Ubuyashiki elaborating on the plan involving Yohan. After hearing the full picture—the Blue Spider Lily, Tamayo's defection, the battle in Asakusa—the Pillars finally understood the importance of the plan and gave it their full support.

"I figured you'd stay over there and have dinner with the Pillars," Yohan commented as he watched Kanae stuffing food into her mouth.

"Mmmph… Yohan, you have no idea how boring it is to eat with the Pillars," Kanae replied with a puffed-out cheek.

"Well, when you put it that way…" Yohan chuckled, imagining the assorted eccentric personalities of the Pillars all forced around one table. Maybe she had a point.

"Um... Yohan, I have something to talk to you about."

"Swallow your food first."

Yohan was beginning to notice something—after spending so much time together, Kanae seemed to be changing a little. She was more casual, more expressive… more herself.

"Right. So, Yohan, the Master has a request. He'd like you to teach the Pillars how to use Tekkai."

"Only Gyomei Himejima and Tengen Uzui have managed to get the basics down, but the others are all stuck."

"Can't you teach them?" Yohan raised a brow. He distinctly remembered Kanae reaching the entry level of Tekkai herself not long ago.

"Well... I did manage it, but I think that was only because I'd eaten your food back then and my constitution improved dramatically." Kanae admitted this shyly. "So to be honest, I don't really know how to teach it."

"Makes sense." Yohan thought for a moment. "Alright, I'll have Mitsuri help you instruct them."

"Gulp gulp gulp." Mitsuri was busy downing soup when she heard her name.

"W-Who's calling me?" she asked cautiously, eyes darting around as if someone was about to steal her food.

"Mitsuri, when you've got some free time, go with Kanae to the Demon Slayer HQ and help the other Pillars with their Tekkai training."

"Sure! Leave it to me!" Mitsuri beamed, happy for a chance to be helpful to Yohan.

Kanae had no objections. She knew Mitsuri's Tekkai training had progressed well, and going with her meant there wouldn't be any conflict with the other Pillars.

"But Kanae," Yohan added, "let the Master know that Mitsuri should also be allowed to observe the other Pillars' Breathing Styles."

"Consider it her compensation for helping out."

"Of course. I'll make sure the Master is aware."

Mitsuri stuck her tongue out playfully. She understood Yohan was doing this for her benefit. The more styles she saw, the better she'd be able to develop her own.

In the days that followed, Mitsuri frequently accompanied Kanae to the Demon Slayer HQ. There, she diligently instructed the other Pillars. Of course, she only explained things—Mitsuri refused to spar with anyone except Yohan. Training bouts were reserved for him alone.

Unlike her bubbly behavior around Yohan, Mitsuri became entirely focused and serious when she was working. Her goal was to finish the task efficiently and thoroughly.

The Pillars who hadn't yet grasped Tekkai began training even harder. If even one of the girls at Yohan's side could master such a powerful technique, then they—elite warriors—had no excuse.

What they didn't know, however, was that Mitsuri's rapid progress came largely from her unique, naturally powerful constitution.

As the days rolled by, Mitsuri's visits to HQ became less frequent. She would occasionally drop in to give advice but stopped going daily.

During this time, Sanemi Shinazugawa finally regained consciousness. Upon learning that he'd been defeated in a single move, he fell silent. There was nothing more to say.

One day—

"Yohan, when are you going to fetch the Blue Spider Lily you mentioned?"

This was the sixth time Shinobu had asked the same question that day. Without the flower, neither her research nor Tamayo's could move forward.

"The Blue Spider Lily, huh... I suppose it's time," Yohan said.

It was a flower that only bloomed sporadically during the day once a year. Yohan didn't actually know where to find it. So he'd negotiated with the system to have it included as a reward for his next task.

Fortunately, he succeeded. The system, after all, existed to serve him—and just a few days ago, it had already begun alerting him to prepare for departure.

"Mitsuri, I'm heading out for a bit. You'll stay here at the Butterfly Mansion, okay?"

"Yohan, will you be gone long?"

"No, just stepping out to pick something up. I'll be back before you know it."

"Alright then, I'll stay here! But you better come back soon!" Mitsuri grinned and waved, understanding the real message behind Yohan's request.

"Of course."

Yohan indeed wanted her to stay behind. The journey would take him through some rough, remote terrain. He'd be quicker and safer moving alone. The mountain wilderness could be harsh and unpredictable—he didn't want Mitsuri to have to endure it.

And so, with one last look at the mansion, Yohan quietly set off to find the elusive Blue Spider Lily.

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