Later same bookNi Jianyi (to Jien) wrote:Unless a certain someone was trying to atone for his past ability to save a baby brother. Particularly when said brother wished only for love, and yet recieved oppression. Plus you screwed your mother. Do calm yourself Sha Jien.
And Jien is her real, full son.Sha Jien to Yaone wrote:There were times when, to calm her (Jien's Mother) down, I took my dead father's place and slept with her
Things like that are fairly common in Saiyuki. (specifically the original manga)