In 608, Imoko returned with HAI Seisei (an envoy of the Sui Dynasty) without a reply letter from Emperor Yodai of Sui, as Imoko had lost it in Kudara (Paekche in early Korea) on his way back (there are many theories regarding the loss of the letter, one of which asserts that the letter had such a horrible content that Imoko couldn't show it to the Emperor of Japan).
推古天皇16年(608年)に裴世清を伴って帰国、ただし煬帝の返書は帰路に百済において紛失した（紛失に関しては諸説あり、とても見せることが出来る内容ではなかったからであるとする説もある）。