Ryu Mitsuse (光瀬龍 Mitsuse Ryū?, March 18, 1928 – July 7, 1999) was a Japanese science fiction writer. In the West he might be best known for manga-related works and the story The Sunset, 2217 A.D. which appeared in Frederik Pohl's Best Science Fiction for 1972.
Mitsuse was born at Minami-Senju, Kita-Toshima District, Tokyo Prefecture in 1928. His birth name was Chiba Kimio (千葉 喜美雄?). After marriage he adopted his wife's surname as his surname, taking the name Iizuka Kimio (飯塚 喜美雄?).
He went to Tokyo in 1948. He entered into various schools, that is, the Toyo University and the Meiji University. But he stayed there for several months. He entered into Kawamura High school in 1948, and graduated from this school. He entered into the Department of agriculture in the Tokyo University of Education in 1949. He graduated from the Department of science of this university in 1953.
Mitsuse joined Kagaku Sousaku Club where Takumi Shibano was operating as a publisher and an editor of the Fanzine Uchuu-jin. He started publishing various short novels in the fanzine Uchuu-jin (宇宙塵?) under the pen-name Mitsuse Ryu.
As an SF novelist, he created the Space Chronicles series. His early long SF novel Tasogare ni Kaeru (黄昏に還る) belongs to this series. Most of his short SF stories constitute this series. Rakuyou 2217 nen (落陽2217年, The Sunset, 2217 A.D.) is one of these stories.
In Japanese science fiction he might be better known for the novel Ten Billion Days and One Hundred Billion Nights (百億の昼と千億の夜?), which combines interest in technology and the Buddha. It was ranked the top of the Japanese SF novels in a 2006 poll by the SF Magazine. Ten Billion Days and a Hundred Billion Nights was adapted into a manga by Moto Hagio in the late 1970s.
- Tasogare ni Kaeru (たそがれに還る) 1964, Hayakawa Shobou
- Hyakuoku no Hiru to Sen'oku no Yoru (百億の昼と千億の夜) 1967, Hayakawa Shobou.
- English translation: Ten Billion Days and One Hundred Billion Nights, 2011, Haikasoru.
- Kan'ei Mumyouken (寛永無明剣) 1969, Rippu Shobou
- Ushinawareta Toshi no Kiroku (喪われた都市の記録) 1972, Hayakawa Shobou
- Seitou Totoku-fu (征東都督府) 1975, Hayakawa Shobou
- Hiden Miyamoto Musashi (秘伝宮本武蔵) 1976, Yomiuri Shinbunsha
- Higashi Canal Bunsho (東キャナル文書) 1977, Hayakawa Shobou
- Karera, Atlantis yori (かれら、アトランティスより) 1979, Rippu Shobou
- Uchuu Kouro (宇宙航路) 1980, Kisou Tengaisha
- Gen'ei no Ballad (幻影のバラード) 1980, Tokuma Shoten
- Karera Seiun yori (かれら星雲より) 1981, Tokuma Shoten
- Shin Miyamoto Musashi (新宮本武蔵) 1981, Tokuma Shoten
- Tokoro wa Izuko, Suishi-ei (所は何処、水師営) 1983, Kadokawa Shoten
- Heike Monogatari (平家物語) 1983 - 1988, Kadokawa Shoten
- Fubuki no Niji (吹雪の虹) 1984, Shuueisha
- Aurora no Kienu Ma ni (オーロラの消えぬ間に) 1984, Hayakawa Shobou
- New York, Yousoro (紐育（ニューヨーク）、宜候（ようそろ）) 1984, Kadokawa Shoten
- Sabita Ginga (銹た銀河) 1987, Hayakawa Shobou
- Miyamoto Musashi Kessen-Roku (宮本武蔵血戦録) 1992, Koufuusha Shuppan
- Yamiichi no Shinkirou (闇市の蜃気楼) 1993, Jitsugyou no Nihonsha
- Hidedyoshi to Nobunaga - Shisetsu Shinchou-kou-Ki (秀吉と信長 私説 信長公記) 1996, Koufuusha Shuppan
- Ihon Saiyuuki (異本西遊記) 1999, Kadokawa Haruki Jimusho
- "Hayakawa's SF Magazine's All-Time Best SF". Locus Magazine. Retrieved February 10, 2012.