After this stage he became the disciple of Saicho, and in 804 he crossed over to Tang China with Saicho as an interpreter of Chinese; he returned to Japan after receiving both the Endon precepts from Daosui (a Chinese Tiantai (Tendai) monk) and the dharmic transmission of Vajrayana (esoteric) rituals from Shunxiao, exactly as Saicho did.
その後最澄に師事し、804年（延暦23年）中国語の通訳として最澄とともに唐へ渡り、最澄と同じく道邃（どうすい）から円頓戒を、順暁（じゅんぎょう）から密教の付法をうけ日本へ帰国した。