Seoyichi, also known as the Western Bastion, is a Chiseong constructed between the Seojangdae or the Western Artillery and the Seoporu or the Western Command Post. "Chi" refers to a pheasant, symbolizing soldiers who could conceal themselves like pheasants within the Chiseong before launching attacks against enemies approaching the fortress walls. Hwaseong Fortress, encompassing 10 bastions, features Seoyichi, which is relatively small compared to the other bastions due to its location on a steep slope leading to the summit of Paldal Mountain.

Originally, Seoichi was built in 1796 in the 20th year of King Jungjo of the Joseon Dynasty, and it was restored in 1975 by retaining its original appearance. Various sized stones with a reddish hue are still well preserved, and a rectangular stone, larger than the flat wall, was positioned in the lower part to provide additional support.