What killed the real Hikaru?

What killed the real Hikaru in "The Summer Hikaru Died" remains deliberately ambiguous throughout the series, reflecting the manga's focus on psychological horror rather than explicit explanations.

The Mysterious Circumstances

The manga establishes that the original Hikaru died in the mountains during summer, but author Mokumokuren intentionally leaves the exact cause of death unclear. This narrative choice emphasizes the story's central themes of grief, identity, and acceptance rather than providing concrete answers about the supernatural events.

Clues and Implications

Several hints throughout the series suggest Hikaru's death was connected to the mysterious mountain entity that later takes his form. The mountain itself appears to be a supernatural location where normal rules don't apply, and various characters reference strange occurrences and disappearances in the area over time.

The entity that becomes "Hikaru" seems to have absorbed or consumed the original in some way, gaining access to his memories and personality traits. However, the process isn't clearly defined as either violent or peaceful—it exists in the realm of cosmic horror where human understanding falls short.

The Author's Intent

Mokumokuren's decision to keep Hikaru's death ambiguous serves the story's deeper purpose. Rather than focusing on the mechanics of death, the manga explores how Yoshiki processes loss and forms a new relationship with something that resembles his deceased friend. The mystery surrounding the original death forces readers to confront uncomfortable questions about identity, memory, and what makes someone "real."

Theories and Speculation

Fans have theorized everything from accidental death during hiking to supernatural consumption by the mountain entity. Some suggest Hikaru may have been drawn into the mountain's otherworldly influence, while others propose he simply died from natural causes before the entity discovered his body.

The true cause of Hikaru's death may never be fully revealed, leaving readers to grapple with the same uncertainty that haunts Yoshiki. What other mysteries do you think the series will unveil as it continues?