This article explores why twins are so rare in Japan, with the main contributing factors being its low fertility rate and cultural beliefs surrounding twins. It also compares twin births in other countries to those in Japan and examines the role of medical advancements and assisted reproductive technologies. According to data from The World Factbook published by The Central Intelligence Agency (CIA), Japan has the second-lowest twin birth rate among all countries included in this analysis, and while medical advancements may help increase twin birth rates slightly over time, it is unlikely that they will drastically change how common twins are within Japanese society any time soon.