Muzan: My daughter can't be that weak!

"Teacher, teacher, Yukina's here!"

Yukina walked into the Japanese-style room with a clattering sound; before she could even stand properly, her voice arrived first.

Kokushibo was kneeling beside a low table, with a chessboard in front of him, on which black and white chess pieces were scattered in an orderly fashion.

His black piece hovered in mid-air, as if he were contemplating his next move.

Hearing the noise at the door, he paused, and his six eyes slowly rose to look at the small head whose hair was still a little messy from running too fast.

Recently, he has been spending more and more time in the Infinite Castle because he is teaching Setsuna.

The once empty Japanese-style room has gradually become filled with traces of life.

A small cushion appeared next to the low table, a stack of calligraphy practice papers was added to the corner, and a doodle that Xue Nai had given him last time was even hanging on the wall. It depicted him and a strange-looking animal, which she said was "the most amazing teacher and the cutest little dog."

Kokushibo also asked Nakime to expand the courtyard and create another spacious training ground next to it.

"Teacher, what is this?"

Yukina ran over to Kokushibo in a few steps, sat down next to him with her knees together properly, but her eyes were fixed on the round pieces on the board, full of curiosity.

Hei Shibo put the black stones back into the go board basket in a slow and deliberate motion.

"...Go," he replied.

"What is Go? Is it for playing? Why are these black and white stones here? Do they fight? Who wins?"

She tilted her head, glancing at the chessboard one moment and then at the black chess piece the next.

Kokushibo lowered his eyes and answered one by one.

Xue Nai's eyes lit up as she listened, her face showing eagerness to try.

Kokushibo observed her expression, pursed his lips, and after a long pause, slowly spoke:

"...After...you've finished...today's...lessons, I...can...teach you..."

"Really?!"

With her eyes crinkling into crescents, she immediately straightened her back, took the slightly curled booklet from her bosom, and placed it neatly on the table.

She cleared her throat, placed her small hand on the booklet, and began to speak earnestly:

"Teacher, let's begin! I can't wait—!!"

Kokushibo nodded slightly and opened the booklet to the section he had been taught last time.

The two ghosts continued their routine of reviewing old acquaintances and learning new knowledge.

Ever since she pretended to know what she didn't, whenever she encounters something she doesn't understand, she obediently asks, "Teacher, why is this happening here?"

Kokushibo then stopped and patiently explained until she nodded and said she understood.

Today's lesson will end soon.

Kokushibo closed the booklet, got up and walked to the bookshelf on the side of the room, preparing to take the Go set on the top shelf.

While he turned his back, Xue Nai immediately pulled out the wad of cotton thread that she had stuffed into her clothes.

Before leaving, she dragged her brother along to practice twice more!

This time I'm sure I can find the perfect little spider to show the teacher!

She had her back to Kokushibo, her small hands fiddling behind her back, her ten short fingers twisting and turning.

Wait, something's not right about this step...

She frowned, untied the thread, and started again.

Okay, okay, this time it should be right...

Wait, this seems to be...

She was so anxious that the tip of her nose started to itch.

Black seized the chess basket and chessboard, then turned around.

He immediately spotted the small figure with its back to him, fiddling with something.

Given Xue Nai's height, he could easily see that she was trying to play cat's cradle, but it didn't seem to be going well, as she kept getting herself into a dead end.

Yukina felt the gaze on her back.

She turned her head and glanced quickly at Kokushibo, instinctively hiding her hands behind her back.

Then she secretly glanced at her hands.

Hey, it's done!

Her eyes lit up, and she immediately took her hand out from behind her back and raised it high in front of Kokushibo.

"Teacher! Look!" Her voice held a hint of pride. "It's a little spider!"

Between ten short fingers, a crooked, cotton-thread spider is held.

The mesh size was still varied, but it was much neater than the one from this morning. At least it was easy to recognize at a glance as "Ah, it's a spider" rather than "What is this tangled mess?"

Kokushibo lowered his head, his six eyes lingering on the knot of thread for a moment.

Then he reached out and gently placed his hand on the top of Yukina's head.

When that large hand covered her, Yukina felt a warmth that belonged to her teacher.

She remained obediently still, her eyes curving into two small crescent moons.

"...Very good," said Kokushibo.

Kokushibo sat down again beside her, placed the Go board between them, and began to teach the basic rules of Go.

"The chessboard... has nineteen lines in each direction... and a total of three hundred and sixty-one lines..."

He spoke slowly, pausing briefly after each section to look at Xue Nai's face and make sure she was following.

At first, Xue Nai sat upright, her little hands neatly placed on her knees, her eyes fixed on the chessboard.

But as Kokushibo's explanation went deeper, her posture began to change little by little.

First, my back isn't as straight anymore.

Then her little hand moved from her knee to the edge of the chessboard and curiously touched the smooth chess pieces.

Then, she began to rest her chin on her hand, tilting her head slightly as if deep in thought.

"Do you understand this part?" Kokushibo stopped explaining and turned to look at her.

Xue Nai blinked, her eyes filled with a clear sense of foolishness.

"Teacher," she honestly admitted, "Xue Nai doesn't seem to understand very well..."

Kokushibo repeated what he had just said.

This time, he slowed down even more, breaking down each key point and gesturing with his fingers on the chessboard to show her.

Xue Nai focused her attention, her little hands unconsciously moving from her chin to her knees. She leaned forward slightly, her little brows furrowed, and she stared intently at the black and white chess pieces.

"...Do you understand now?"

After Kokushibo finished speaking, he asked again.

Yukina stared at the chessboard for a long time before finally nodding as if she understood.

"Hmm... Yukina understands!" she said confidently, but her still somewhat dazed eyes betrayed her.

Kokushibo did not continue speaking.

He glanced outside, then looked back at Xue Nai.

"From now on... you can come here every other day," he said.

Yukina paused for a moment, tilted her head, and asked with a wronged look, "Why? Doesn't the teacher want to see Yukina every day?"

Kokushibo did not provide a detailed explanation.

"Without studying every day... you won't remember it well. It's better to leave some time every other day to think about it yourself."

Xue Nai thought about it and felt that what the teacher said made a lot of sense.

She didn't ask any more questions, but simply looked up and obediently replied, "Okay."

Actually, she was still pondering the rules of Go in her mind.

What's with the anger? What's with the eyes? How can black and white pieces fight each other?

A complete mess.

Kokushibo has no intention of leaving Infinity Castle today.

He stood up and walked towards the newly opened corridor on one side of the Japanese-style room, which led to the training ground that he had asked Nakime to build.

Yukina stood up with him, walked out of the room, and found that the teacher had turned to the other side.

"Where is the teacher going?" she asked, looking up in confusion.

"...training ground."

After Kokushibo finished speaking those three words, he received a longing look in his eyes.

Kokushibo remained silent for a moment.

Then he reached out his hand.

Yukina looked down at the large hand extended in front of her, paused for a moment, then chuckled and put her small hand into the teacher's palm.

The two ghosts walked hand in hand toward the training ground.

Throughout the journey, Xue Nai's little mouth never stopped.

"Teacher, is your training ground newly built? How big is it?"

"Teacher, look! That room over there looks different from the one I saw last time!"

"Huh, Yukina doesn't think she's ever walked this road before... Is it a new road? Where does it lead?"

She looked left and right, her little hand holding Kokushibo's finger, hopping and skipping forward. Occasionally, when she encountered a step, she would jump up, dangling in the air for a moment before landing steadily.

Hei Si occasionally hummed in agreement, but his footsteps always kept pace with hers.