When Kukai returned from Tang one year later after Saicho had returned, Saicho recognized that the Esoteric Buddhism he had learned in Tang from Jungyo was collateral and asked Kukai with the utmost courtesy to take him in as a disciple in order to study Esoteric Buddhism, but he eventually parted from Kukai due to their differences in views on Buddhism.
しかし最澄が帰国して一年後に空海が唐から帰国すると、自身が唐で順暁から学んだ密教は傍系のものだと気づき、空海に礼を尽くして弟子となり密教を学ぼうとするも、次第に両者の仏教観の違いが顕れ決別した。