As the Demon Slayer Corps focused on gathering information about Muzan, Shun approached Tamayo with a purpose.
He had previously acquired the blood of Akaza and Doma, which could potentially expedite her research.
When Shun arrived at her clinic, a soft, agonized groan reached his ears.
"Uuuaaahhhhhhh..."
The pained sound echoed through the room, muffled by the clinic's soundproofing. Otherwise, Tamayo's cries of distress might have filled the entire manor.
Her entire body was flushed pink, cold sweat pooling on her back and soaking through her thin kimono, accentuating her mature figure.
Tamayo was clearly in agony—her toes curled, her brow furrowed, and she clutched her chest as if in unbearable pain.
Shun quickly assessed the situation. Entering the room, he noticed various vials and concoctions strewn across the table.
"Lady Tamayo, were you experimenting on yourself?"
Her anguished expression raised alarm in Shun's heart.
He rushed to her side, gently lifting her upper body into his lap. As he wiped the sweat from her forehead, he loosened the upper part of her kimono.
Sure enough, swollen purple veins snaked across her pale skin. Pressing a hand to her chest, Shun felt her heart pounding frantically, as though it might burst.
If it were merely physical damage, her demon physiology could handle it, but the problem ran deeper. Her mind and body were under immense strain.
In the world of Kimetsu no Yaiba, demons were born from Muzan's blood, which carried immense spiritual energy. This energy often created a dichotomy between a demon's human soul and its demonic essence.
Though Tamayo had broken free of Muzan's control, remnants of his influence remained within her body. Now, as she tested the humanizing serum, her physical and spiritual energies clashed violently.
"Lady Tamayo, you're in danger!"
Shun began channeling his Mystical Palm Technique to stabilize her body.
"Stay conscious and focus on the warmth of my hands. If anything feels wrong, let me know immediately." He instructed.
Despite her pain, Tamayo nodded weakly, closing her eyes to concentrate. Slowly, she felt the heat from Shun's hands permeate her body, bringing both pain and comfort.
"Ah... it's so... hot..." She murmured, her voice trembling.
The restorative energy flowed through her, mending her physical injuries. But as her body healed, the mental struggle grew more apparent.
Shun frowned. "If this were a mental attack, I could counter it with my Mangekyo Sharingan... but this is a battle between body and soul."
Seeing her eyes losing focus, he made a swift decision. Activating his Master-Slave Contract, he infused his chakra into her, forming an unbreakable bond.
"Lady Tamayo, I'm using magic to stabilize your soul. Trust me." He said firmly.
Under the contract's influence, the demonic energy within Tamayo was subdued. The humanizing serum took full effect, allowing her transformation to complete.
Tamayo's breathing steadied as her body began to cool. Slowly, she opened her eyes and looked at Shun with gratitude.
"Thank you, Takema-kun. Without you, I might have lost myself." She said softly.
Shun hesitated. "Lady Tamayo... there's something you need to know."
He glanced at her, his expression conflicted. "Because of the Master-Slave Contract, I am now your master. Your life and death are tied to my will."
Pausing, he continued, "If you ever harbor ill will toward me or defy my commands, the contract's backlash will be severe."
Tamayo's face darkened at the revelation. Though she had escaped Muzan's control, she was now bound to Shun.
Yet, before she could fully process her emotions, a sudden jolt shook her. Both she and Shun froze.
The contract had triggered its backlash—Tamayo's residual negative feelings toward Shun had set it off.