On the western edge of Edo Castle (the current Emperor’s Palace), this gate leads directly to the Koshu Highway. The gate’s name comes from Hattori Hanzo Masanari and another Hattori Hanzo Masanari, a father and son who headed security there. Because his subordinate, Igamono Doshin was given a house outside the gate in Yotsuya, it is said to have been the gate that the Shogun escaped from in times of emergency.