A new and distinct cultivar of Chrysanthemum plant named `Yosun City`, characterized by its uniform and somewhat outwardly spreading plant habit; strong and freely branching growth habit; dark green-colored foliage; uniform flowering response and habit; typically grown as a spray-type; early flowering habit; large daisy-type inflorescences with elongated oblong-shaped ray florets; red and yellow bi-colored ray florets; and excellent postproduction longevity with plants maintaining good substance and color for about four weeks in an interior environment.