At the end of World War I, a group of foreign exchange students studied mathematics at Princeton University in the peaceful country of America. Chinese student Wen Wei Jun and Japanese student Shan Ben Kang Fu were roommates and close friends who survived a love triangle involving fellow classmate Qing Tian Xiu, a beautiful, intelligent and kind Japanese girl with royal roots. However, years later, with the outbreak of World War II and China at odds with Japan, the two friends, and now expert code-breakers are forced to become archrivals.