In Episode 9 of "The Summer Hikaru Died," we are plunged into Yoshiki's recollection of a ritual conducted in honor of the Indo family ancestors, possibly even Hikaru’s father. As Yoshiki frets over whether Hikaru is feeling downcast, Hikaru is, in reality, lost in contemplation about swiping a few of the mushroom bun offerings.
Fast-forwarding to the present, Yoshiki and Hikaru find themselves at Kurebayashi’s abode, with Hikaru peacefully slumbering on the sofa. Seizing this golden opportunity, Yoshiki endeavors to glean some crucial information, such as the nature of the entity they encountered in the diner. It turns out to be an impurity—a spectral being whose emotions surge forth uncontrollably when the fragile veil separating the realms is rent asunder.
Yet, Hikaru himself acts as a veritable lightning rod for such spirits. During his time on the mountain, he amassed them, but now that he's residing in the village, there seems to be an unprecedented influx of impurities. Throughout this revelation, Yoshiki is comforted to learn that it is not Hikaru but the impurities that are the source of all the turmoil.
An uneasy Hikaru eventually stirs from his slumber, and Yoshiki's concern mounts, fearing what Hikaru might do next. Kurebayashi manages to soothe the tensions by presenting Hikaru with mushroom buns. She then becomes an audience to the Hikaru-Yoshiki dynamic, as one berates the other. Kurebayashi recounts the harrowing tale of her husband rising from the grave, only to harm their child. It appears her husband also felt remorse for causing pain because it wounded the object of his affection. They concur that Hikaru is distinct; whereas Kurebayashi’s husband’s soul lingered within, Hikaru transcends the mere cycle of life, death, and rebirth.
Kurebayashi then inquires about their plans concerning the impurities. While Hikaru briefly contemplates fleeing, he realizes he could never abandon Yoshiki, and thus vows to safeguard his home. A taken-aback Yoshiki echoes this sentiment—he yearns to both remain by Hikaru's side and shield the village. Moved by their resolve, Kurebayashi agrees to lend them her aid.
Meanwhile, Tanaka stands toe-to-toe with the malevolent impurity that emerged from the diner. As the creature surges through him, Tanaka is inundated with stolen memories from the boys, his mind's eye catching a fleeting glimpse of Hikaru. As they make their way out, Kurebayashi proposes that they seek the counsel of Elder Takeda. In a hushed tone, he warns Hikaru that if Yoshiki continues to 'mix'—to straddle the line between human and something else—he will eventually lose his humanity altogether.
On the journey home, Yoshiki takes an unplanned detour to mourn the loss of his old friend Hikaru, a secret known only to him, as the world carries on, oblivious to the void left behind. Naturally, Hikaru trails after him, eager to uncover their old haunts and reminisce about the childhood games they once shared. He is consumed with curiosity, wanting to know how he differs from the Hikaru of old. He then poses a delicate question: did Yoshiki harbor romantic feelings for the old Hikaru? With a wistful smile, Yoshiki admits that he doesn't feel that way about this new incarnation of Hikaru. Yet, he also reassures him that he doesn't need to strive to be human, as long as he refrains from taking lives.
The pair returns to their research, theorizing that the famine severed the once-strong bond between the village and Nonuki-sama. They ponder the possibility that Hikaru himself might be a deity, and that the impurities are drawn to him because he abandoned the mountain. Yoshiki vows that they will discover a means to confine the impurities to the mountain, without the need to sacrifice Hikaru in the process.
Their next stop is Takeda's abode, where they concoct a story about a school project as their reason for visiting. Takeda, however, urges them to bring Kurebayashi along, convinced that he will be the next to fall victim. He, too, speaks of the impurities, casting blame on the Indo family. Yoshiki attempts to soothe his fears, but Hikaru senses a sinister presence already lurking within Takeda. As the creature reveals a sword, Tanaka materializes out of nowhere, seizing it from Takeda's grasp. In a swift, merciless motion, he turns and decapitates Hikaru, leaving Yoshiki paralyzed with horror.
Before Yoshiki can fully comprehend the magnitude of the tragedy, an otherworldly substance begins to ooze from Hikaru's severed neck, a sight both grotesque and mesmerizing.
