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. Mokumokuren first conceived of the series while studying for exams and later began posting drawings on Twitter, which led to the Young Ace Up editorial department approaching Mokumokuren to serialize the manga via the Young Ace Up website. As of June 2024, the series' individual chapters have been collected into five tankōbon volumes. An anime adaptation has been announced.

Upon release of the first volume, the series became a critical and commercial success, with the first volume selling 200,000 copies in three months, and received critical praise for story, artwork, and characters.

Yoshiki and Hikaru are two teenage boys living in a small town in rural Japan. Despite having opposite personalities and different hobbies, the two maintain a close friendship. However, on one winter day, Hikaru is fatally injured while hiking in the mountains alone. Before dying, a mysterious eldritch being comes across him and consumes him, becoming him physically in the process. This "Hikaru" has all the feelings and memories of the original, yet remains a separate being, something Yoshiki realizes rather quickly. Yoshiki still wants to stay with "Hikaru", however "Hikaru"'s alien nature, along with other eldritch beings and hunters of said beings may make that impossible.

Hikaru (ヒカル)

Voiced by: Yōtarō Negishi (vomic, PV1),^[2] Hiro Shimono (PV2),^[3] KENN (PV3),^[4] Junya Enoki (PV4)^[5]

Yoshiki (よしき)

Voiced by: Tomohiro Ohno (vomic, PV1),^[2] Yoshitsugu Matsuoka (PV2),^[3] Tomoaki Maeno (PV3),^[4] Koki Uchiyama (PV4)^[5]

Mokumokuren first conceived the series while studying for high school entrance exams. After graduating, Mokumokuren began posting drawings on Twitter in their spare time in January 2021.^[6] Mokumokuren was later approached by the Young Ace Up editorial department to serialize the manga in Young Ace Up, which they accepted.^[6] Mokumokuren is a fan of action manga from Weekly Shōnen Jump and Weekly Young Jump, particularly Tokyo Ghoul.^[6]

While writing the story, Mokumokuren tries to keep the horror to a minimum by trying to appeal to people's emotions rather than just being scary. Mokumokuren also feels the theme of the story adds to the horror based on the suspension bridge effect, which states that it is easier to fall in love when feeling anxious or fearful.^[6] For the artwork, Mokumokuren tries to use onomatopoeia that are not often used, while also staying cautious to make sure it works properly in the context of the story.^[6]

In the 2022 Next Manga Award, The Summer Hikaru Died ranked 11th in the web manga category. It was also the most popular choice among traditional Chinese voters.^[20] The series topped the 2023 edition of Takarajimasha's Kono Manga ga Sugoi! list of best manga for male readers.^[21] It was also nominated for the 16th Manga Taishō.^[22] The series ranked fifth in the Nationwide Bookstore Employees' Recommended Comics of 2023.^[23] This series also ranked 7th in the 7th Tsutaya Comic Awards.^[24] In 2023, the series was listed by the New York Public Library among its Best Books for Teens that year.^[25] It ranked 29th on the 2023 "Book of the Year" list by Da Vinci magazine.^[26] In 2024, the first volume and series author Mokumokuren were nominated for the Eisner Award for Best U.S. Edition of International Material—Asia and for Best Writer/Artist respectively.^[27]

The first volume received three times more orders than copies available in the first print run.^[28] The volume was reprinted six times in three months, having over 200,000 copies in circulation.^[28] By October 2022, the series had 550,000 copies in circulation.^[29] By June 2023, the series had 1.4 million copies in circulation.^[30] By December 2023, the series had 1.9 million copies in circulation.^[31] By May 24, 2024, the series had 2.1 million copies in circulation.^[32]

Chanmei from Real Sound praised the story and characters as emotional. Chanmei also praised the artwork, believing it complemented the story well.^[1] Tensako Miura from An An praised the story, main characters, and artwork, positively noting the artwork's use of shades of black.^[33]