Series left incomplete due to death of the author/artist
Manga
A not-perfectly-exhaustive list of manga and light novel series left incomplete or discontinued due to death of the/a creator.
Thank you to all the creators who have spent their days bringing us joy and happiness with their lives' work.
Thank you to all the creators who have spent their days bringing us joy and happiness with their lives' work.

Manga, ? vol, 1989
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Author:-
Incomplete at 41 volumes due to Miura Kentaro's 2021 death from an aortic dissection. Perhaps the most icon instance of a series' premature end in the new millenium.

Manga, 7 vol, 2006
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Author:5
Incomplete at 7 volumes due to writer Sato Daisuke's 2017 death from heart disease.

Manga, ? vol, 2015
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Incomplete at 22 volumes due to writer and Dragon Ball creator Toriyama Akira's 2024 death at 68 from acute subdural hematoma. It is unclear if artist Toyotarou intends to continue the manga.
Hi no Tori (1967)
Phoenix

Manga, 16 vol, 1966
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Incomplete at 16 volumes due to Tezuka Osamu's 1989 death from stomach cancer. His last words were "I'm begging you, let me work!" Despite being unfinished, Hi no Tori is widely considered Tezuka's magnum opus; he worked on it for over 30 years.
Maou Gakuin no Futekigousha: Shijou Saikyou no Maou no Shiso, Tensei shite Shison-tachi no Gakkou e Kayou
The Misfit of Demon King Academy: History's Strongest Demon King Reincarnates and Goes to School with His Descendants

Manga, 4 vol, 2018
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Author:-
Incomplete at 4 volumes due to artist Kayaharuka's 2021 death from pancreatic cancer.

Manga, 45 vol, 1969
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Incomplete at 45 volumes due to Fujiko F. Fujio's 1996 death from liver failure.

Light Novel, 22 vol, 2004
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Incomplete at 20 volumes at the time of Yamaguchi Noboru's 2013 death from undisclosed causes (likely cancer, with which he was diagnosed in 2011). The final two volumes were ghostwritten based on Yamaguchi's notes and the story is complete, in line with Yamaguchi's intentions.
(Thank you Fabrizio00 for explaining the whole situation to me!)
(Thank you Fabrizio00 for explaining the whole situation to me!)

Manga, 3 vol, 2011
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Author:-
Incomplete due to writer Shinkiba Yuki's 2015 death from complications resulting from cancer treatment.

Manga, 23 vol, 1990
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Incomplete at 23 volumes due to Tada Kaoru's 1999 death from a cerebral hemorrhage caused by a head injury. According to her spouse, the anime adaptation uses Tada's intended ending and made use of her notes.
Crayon Shin-chan
Crayon Shinchan

Manga, 50 vol, 1990
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Author:-
Incomplete at 50 volumes due to Usui Yoshito's 2009 death in a hiking accident. In 2010 a sequel series, New Crayon Shin-chan was launched by members of Usui's creative team.
Hikari to Tomo ni...: Jiheishouji wo Kakaete
With the Light: Raising an Autistic Child

Manga, 15 vol, 2000
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Author:-
Incomplete at 15 volumes due to Tobe Keiko's 2010 death from mesothelioma.
Tatoe Hai ni Nattemo
Though You May Burn to Ash

Manga, 6 vol, 2015
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Incomplete at 6 volumes due to Oniyazu Kakashi's 2019 death from undisclosed causes.
Katsute Mahou Shoujo to Aku wa Tekitai shiteita.
The Magical Girl and the Evil Lieutenant Used to Be Archenemies

Manga, 3 vol, 2013
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Author:-
Incomplete at 3 volumes due to Fujiwara Cocoa's 2015 death from an undisclosed illness.

Light Novel, 6 vol, 2002
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Author:-
Incomplete at 12 volumes (including spinoff books) due to Yamato Takahiro's 2009 death from leukemia.

Manga, 3 vol, 2000
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Author:6
In complete at 5 volumes (including spinoff series Chouhatsu Denkou Sekka Boys) due to Tohjoh Asami's 2007 death from an undisclosed illness.

Manga, 2 vol, 2006
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Author:-
Incomplete at 2 volumes due to Takeda Hinata's 2017 death from undisclosed causes.

Manga, ? vol, 2018
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Incomplete at 9 volumes due to writer Tsugikuru's 2019 death from undisclosed causes (possibly complications from a cerebral hemorrage in 2017). It is unclear if the artist intends to continue the manga.

Manga, 7 vol, 2011
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Author:-
Incomplete at 7 volumes due to Soutsuka Rou's 2014 death from stomach cancer.

Light Novel, 12 vol, 2007
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Author:-
Incomplete at 12 volumes due to Matsuno Akinari's 2011 death from undisclosed causes (likely longterm illness).
Chokomimi
Chocomimi

Manga, 11 vol, 2003
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Author:7
Incomplete at 11 volumes due to Sonoda Konomi's 2019 death from breast cancer.
Shoujo Nemu
Girl Nemu

Manga, 1 vol, 1996
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Author:-
Incomplete at 1 volume due to writer Tsuchiya Garon's 2018 death from undisclosed causes.

Manga, 1 vol, 2017
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Incomplete at 1 volume due to Kajiyama Hiroshi's 2018 death from undisclosed causes.

Light Novel, 15 vol, 2005
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Author:-
Incomplete at 15 volumes due to Yoshino Takumi's 2019 death from undisclosed causes.

Manga, 8 vol, 2017
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Author:-
Incomplete at 7 volumes due to Ashihara Hinako's 2024 death by suicide.

Manga, ? vol, 1993
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Incomplete at 98 volumes due to Saito Takao's 2021 death from pancreatic cancer. It is unclear if his associates intend to continue the manga.

Manga, ? vol, 2018
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Incomplete at 2 volumes due to Morishige's 2020 death from undisclosed causes. Morishige was the penname used by a married couple; which member of the creative team passed away is unknown.

Manga, 3 vol, 2019
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Incomplete at 2 volumes due to Eguchi Kousei's 2020 death from undisclosed causes.

Manga, 19 vol, 2003
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Incomplete at 19 volumes due to Nishi Yuji's 2013 death from stomach cancer.

Manga, 3 vol, 2012
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Incomplete at 3 volumes due to Sadogawa Jun's 2013 death by suicide.

Manga, 1 vol, 1999
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Author:-
Incomplete at 1 volume due to artist Kizaki Hirosuke's 2001 death.
Thank you ArtaRay for bringing this title to my attention!
Thank you ArtaRay for bringing this title to my attention!
Kugutsushi Lin
The Puppet Master Lin

Manga, 14 vol, 2006
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Author:-
Incomplete at 14 volumes due to Wada Shinji's 2011 death from heart disease.

Manga, 20 vol, 2014
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Incomplete at 20 volumes due to Satou Takahiro's 2018 death from heart disease.