A complicated expression flickered across Tamayo's face, and she stepped aside to clear the doorway.
"In that case... please come in." She glanced at the bundle in the Sapphire Star's hand, which radiated a chaotic demonic aura, and already had some idea of Ubuyashiki's intentions.
Although Yushiro remained wary and stared at the Sapphire Star with open hostility, he merely gave a disgruntled huff and stepped aside.
Carrying the bundle containing Kaigaku, the Sapphire Star entered the little courtyard concealed by an exquisite Blood Demon Art. The interior was unexpectedly clean, with a faint, bitter herbal fragrance in the air. Several wooden shelves against the walls held assorted bottles, jars, and books. It looked more like a secluded physician's home than a demon's lair.
Tamayo led them into a well-lit, airy side room that seemed to be used for treating patients. A wooden bed covered with a white mattress stood out.
"Miss swordswoman, please put him here," Tamayo said, pointing to the bed.
"Sure. Just call me Sapphire Star."
The Sapphire Star set the bundle on the wooden bed, untied the knots, and peeled back layer after layer of thick silk, exposing Kaigaku's neither-human-nor-demon body beneath the lamplight.
Tamayo approached the bed and carefully examined Kaigaku's condition and the strange sealing spike in his chest. It was identical to the spike in the Lower Rank demon's head that Tanjiro had asked Chachamaru to deliver earlier, firmly suppressing the demon's regeneration.
Tamayo drew a deep breath and turned to the Sapphire Star. "Miss Sapphire Star, this spike... it has an astonishing ability to suppress demonic regeneration. This may be the key to unraveling the secret of Muzan's immortality, and even to dealing him a truly devastating blow someday!" Her voice trembled slightly with excitement.
"For my research... could you provide another