| 1949 | Born in Kyoto | 
| 1972 | Participated in Bokujin exhibition for the first time, showing Trace *Exhibited every year thereafter in the Tokyo (spring) and Kyoto (autumn) Bokujin exhibitions
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| 1972 | Exhibited in the Bokujin Kansai exhibition in Kyoto *Works shown every year thereafter in the Bokujin Kansai exhibition in Kyoto
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| 1972 | Began studying under Shiryu Morita | 
| 1978 | Organized the Yaku (“Dance”) Calligraphy exhibition and began publishing the magazine Yaku (“Dance”) | 
| 1984 | Admitted to the Bokujinkai (People of the Ink Society) for his work Root | 
| 1986 | Exhibited in the Kyoto Invitational Art exhibition and in several subsequent years | 
| 1990 | Organized the first Soryū exhibition, which has been held every year until the present, with other students of Morita Shiryū | 
| 2000 | Presented at the Bokujinkai New Year study meeting on the theme, “How to move to the fullest” | 
| 2003 | Compiled Rinshosen (Selection of Morita Shiryū’s Exemplary Calligraphic Models), Volume 1 (published by Soryūsha) | 
| 2004 | Compiled Rinshosen (Selection of Morita Shiryū’s Exemplary Calligraphic Models), Volume 2 (published by Soryūsha) | 
| 2005 | Compiled Rinshosen (Selection of Morita Shiryū’s Exemplary Calligraphic Models), Volume 3 (published by Soryūsha) | 
| 2007 | Exhibited in the Sho-no-mori (“Forest of Calligraphy”) exhibition in Kyoto *Works shown every year thereafter in this exhibition
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| 2008 | Work shown in the School of Hidai Tenrai exhibition in Saku, Nagano | 
| 2009 | Exhibited in the World Calligraphy Biennale in Jeonju, Korea | 
| 2009 | Work shown in the Japan Contemporary Artists exhibition in Girona, Spain | 
| 2011 | Presented at the Bokujinkai New Year Study Meeting on “Viewing Bokujin works” | 
| 2012 | Exhibited in the Mono show / M50 Creative Space, Bund1919 in Shanghai, China | 
| 2012 | Edited Sōki: Morita Shiryū nōto (Recollections and Notes on Shiryū Morita; published by Bokujinkai and Sōryūsha, edited by Inada Sōsai) | 
| 2013 | Exhibited in the NAU 21st Century Art exhibition, Tokyo Metropolitan Museum *Works shown every year thereafter in the NAU 21st Century Art exhibition
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| 2013 | Calligraphy commissioned for the Main Gate and Main Hall of Myōkō-ji Temple | 
| 2013 | Compiled BOKUJIN INADA SŌSAI, Vol. 1 | 
| 2015 | Exhibited in the World Calligraphy Biennale in Jeonju, Korea | 
| 2015 | Launched website https://inadasousai.com/ | 
| 2016 | Exhibited in the Kyoto Kunst Köln exhibition in Köln, Germany | 
| 2017 | Exhibited in the Kyoto Kunst Köln exhibition in Kyoto | 
| 2019 | Held exhibition Works by BOKUJIN INADA SŌSAI at the Museum of Kyoto | 
| 2019 | Compiled BOKUJIN INADA SŌSAI, Vol. 2 | 
| 2019 | Compiled and edited Morita Shiryū Catalogue Raisonné: 1952-1998 (Morita Shiryu zen sakuhin shu) (published by Sōryūsha)
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| 2023 | Held the Morita Shiryū & Inada Sōsai Master-Disciple Exhibition Contemporary Calligraphy Commendation Series Second Edition at the Ginza Nagai Garou Planning | 
| 2023 | Held the Recent Works Exhibition of Inada Sōsai Move the Structure of Characters at the Kyoto Takashimaya Tsutaya Bookstore | 
| 2024 | Lecture at Kyoto University of Arts correspondence course |