The Summer Hikaru Died - Episode 1 plunges headlong into a scene of rain-soaked mountains, where figures dart frantically in search of Hikaru. Lying prone on the damp earth, his eye bandaged and throbbing, Hikaru is acutely aware of his desperate need for help.
Flash forward six months, to the sweltering heights of July. The boys pause amidst the heat, yearning for a cool respite. Yoshiki, his tone tinged with playful ridicule, teases Hikaru about his linguistic blunders. But his jests abruptly halt as his mind races back to the harrowing week Hikaru was lost in the mountains—a week Hikaru still can't recall.
Hikaru, sensing Yoshiki's solemnity, attempts to lighten the mood by jesting about Yoshiki's supposed longing for his return. But Yoshiki remains steadfast, finally voicing the suspicion that has haunted him—could this Hikaru be an impostor?
"Huh? How could you possibly know?" Hikaru's revelation sends shockwaves through Yoshiki. With a plea filled with desperation, Hikaru begs Yoshiki not to expose him, confessing his joy at being human and vowing not to harm Yoshiki. Yoshiki, barely able to catch his breath, reluctantly agrees to keep the secret.
In the depths of night, Yoshiki awakens from a haunting dream of his late friend, his heart heavy with grief. After a moment of introspection, he rises, steeling himself for the day ahead. Shortly thereafter, Hikaru arrives, ready to walk to school together. Yoshiki urges him onward, convincing himself that this Hikaru, whatever his true nature, is better than no Hikaru at all.
Meanwhile, Tanaka, an agent for a mysterious company, is dispatched to an undisclosed location. Elsewhere, within the confines of their school, the boys lend their voices to a choir performance, a makeshift replacement for the canceled culture festival of the previous year. Tanaka, in his report, laments the futility of a century-long search yielding no tangible results. Nevertheless, his words hint at a disturbing discovery: a child seemingly embedded within a wall.
The boys find themselves immersed in a movie in the study hall, one that has replayed in their minds at least a half-dozen times before. Yet, Hikaru claims this is his maiden voyage with the film, and his eyes well up with tears for the plight of the hapless protagonist, a reaction he can scarcely contain. As the credits roll, they stroll home with the nonchalance of any other day, the children engaging in their usual pastimes while the villagers carried on with theirs.
Halting at a familiar snack stand, Hikaru indulges, his memory vividly recalling the flavor yet experiencing it anew. His exclamation betrays his awe; for him, this is his inaugural journey as a human. Could he have once been a phantom, wandering the earth unseen? Hikaru ponders, but the notion seems amiss—perhaps a monster lurking in the shadows of his past?
Yoshiki's inquiry into Hikaru's desires for their next adventure catches him off guard, delighting him that Yoshiki seeks his companionship. Their conversation is interrupted by a local feline's sudden distress at Hikaru's presence, and a passerby woman shivers, her spine tingling with an inexplicable chill. Suddenly, an emergency alarm pierces the air—or is it merely a phantom sound within Yoshiki's mind? Hikaru expresses a desire to revisit their spot to continue their manga, a wish Yoshiki eagerly grants.
From the shadows emerges an elderly woman, her screams piercing the air as she speaks of Nonuki-sama descending from the mountain. Her eyes, wide with terror, lock onto Hikaru. Yoshiki urges him onward, yet the question escapes his lips, unable to be contained: Is Hikaru truly among the departed? Hikaru confirms that, though his flesh is real, his soul has transcended mortality. He speaks of finding Hikaru on the brink of death, his memories hazy beyond that point. He reveals his previous numbness to sensation, now replaced by an awareness that began with Hikaru and has led him to this unprecedented existence.
As they bid each other farewell, Yoshiki poses the ultimate question: Do you care for me? Hikaru's affirmation leaves Yoshiki speechless, for such words have never crossed his lips before. He pleads with Hikaru never to abandon him again.
Later, Hikaru awakens to the discordant sounds of his parents' argument, while simultaneously, the same elderly woman is visited by an unseen presence that has already infiltrated her home. Police officers interrogate her daughter, who confirms the tragic news of her mother's passing. The elderly men of the village whisper amongst themselves, fearing they may be next. One reaches out to Tanaka for aid, despite his reluctance. Sensing the villagers' ignorance of the impending peril, Tanaka decides to intervene, determined to uncover the truth lurking in their midst.
