Tokuitsu (c. 760 - 835) was a Hosso sect monk of Japanese Buddhism who lived from the Nara period to early Heian period. His father was FUJIWARA no Nakamaro (EMI no Oshikatsu), and Tokuitsu is said to be his eleventh son. Tokuitsu, which is written as "徳一," may be written as "徳溢" or "得一." There are various theories as to the dates of his birth and death; according to 'Nanto Kosoden,' he was born in 749 and died on August 23, 824.
Tokuitsu is considered to have learned the Dharmalogy of the Hosso Study from Shuen and other monks at Todai-ji Temple first, and moved to Togoku (the eastern part of Japan, particularly Kanto region) at the age of 20 or so.
Although in 815 he was asked by Kukai to transcribe by handwriting and propagate scriptures of Esoteric Buddhism, Tokuitsu sent 'Shingon-shu miketsumon' (eleven clauses of criticism of Shingon Esoteric Buddhism) to Kukai (Kukai did not respond to 'Shingon-shu miketsumon' sent from Tokuitsu.)
(In fact, it was 500 years later that the Shingon sect argued against 'Shingon-shu miketsumon.')
Tokuitsu criticized the Tendai doctrine, beginning with criticisms against 'Bushosho' (excerpt of Buddha nature), and had one of the major Buddhist disputes with Saicho from around 817, called Sanichigonjitsu soron (or 'Sanjo ichijo gonjitsu ronso').
During this time, Tokuitsu built many temples across the southern part of Mutsu Province to Hitachi Province, including Enichi-ji Temple in Aizu in Mutsu Province, Shojo-ji Temple in the same Province, Chuzen-ji Temple (Omido) on Mt. Tsukuba in Hitachi Province (Tsukuba City), and Saiko-in Temple, and at the same time conducted propagation among the people, which reportedly led them to refer to him as 'Tokuitsu Bosatsu,' Bosatsu (Bodhisattva) meaning one who vows to save all beings before becoming a Buddha. Currently, Gorinto, which is said to be the grave of Tokuitsu, remains at the site of Enichi-ji Temple (Bandai-machi, Yama-gun, Fukushima Prefecture).