The 4 textbooks (Tokyoshoseki, Kyoikushuppan,, Jiyusha, Ikuhosha) among the Japanese middle-school textbooks that passed screening in March 2010, describe that Saigo Takamori tried to open the door of Chosun through life risking negotiation in the part of Seikanron. This paper critically examined the contents asserted in the Japanese textbook by analyzing related historical records with focus on ``Dispatching Envoy to Korea`` of Saigo Takamori, which is the core content of the ``seikanron``. As the result, it is found out why Saigo volunteered to be a delegate to Chosun in October 1873 was not to open the door of Chosun but to get a justified cause for a war that can divert frustration of Samurai class, caused from the internal reformation, to outside of the country. Especially, the unarmed peace envoy of Saigo was the first step of 2step Chosun invasion plan, which aimed to draw attention of Japanese public opinions for invasion to Chosun by dying amid of negotiation as an unarmed peace envoy.