The Summer Hikaru Died (Japanese: 光が死んだ夏, Hepburn: Hikaru ga Shinda Natsu) is a Japanese manga series written and illustrated by Mokumokuren. It began serialization on Kadokawa Shoten's Young Ace Up website in August 2021. As of July 2025, the series' individual chapters have been collected in seven tankōbon volumes. It follows the story of Yoshiki, a teenager in rural Japan who discovers that his best friend Hikaru has been possessed by an otherworldly entity, forcing him to navigate their changed relationship amid supernatural dangers.