This article explores the history of blood type in Japan and how it is seen as an important part of a person's identity. It explains the four different types of blood (A, B, AB and O) and how they are associated with certain personality traits. In general, people with type O are seen as reliable, hardworking and honest; people with type A are seen as sensitive and creative; people with type B are seen as passionate and independent; while people with type AB are seen as unpredictable but intelligent individuals who often think outside the box when it comes to problem solving. Although all four types are generally accepted in Japanese society, there is still a preference for those with type A or O due to its perceived positive attributes such as reliability and hard work ethic. Other factors such as gender roles, age, occupation can also influence how someone may be perceived based on his or her respective group.