In Japan, goldfish are a symbol of summer. Around 40 varieties are common, ranging from the beautiful to the comical. A single ranchu―known as the "king of goldfish"―can cost millions of yen. Goldfish have their roots in China, where a genetic mutation produced red carp over 1,500 years ago. How did they become the colorful, diverse fish so beloved in Japan today? In a 5-minute digest, we ask why goldfish are seen as auspicious and introduce their usage as an artistic motif.