Yoritomo Butei was a member of the Mantis Clan. In 1168 he was serving alongside his gunso Yoritomo Satako in a guard tower in Tsuruchi lands. While stationed there they were visited by Tanari, a monk of the Brotherhood of Shinsei. He was accompanied by a nezumi, K'mee, who believed that the building housed something that could be a threat to Rokugan. Satoko did not let them pass until a Emerald Magistrate, Tsuruchi Fusako, arrived there and ordered them to give way. Inside they found a box containing a katana, which K'mee believed to be evil. The blade had a dark fate because of what it would be used for. Fusako and Satoko took it with them and gave it katana to the Mantis Clan Champion Yoritomo Naizen.