It's in the blood

If you've read much manga, you'll have noticed in the little biographies of manga-ka (manga creators) and characters references to astrological sign .... and blood type. In Japan blood type is believed to influence personality.

Create a character for each of the 4 blood types, toss the characters together and see where they take you.

The descriptions are from an article on Japanese Culture by Melanie Shintaku at BellaOnline

Type O
Type O's are outgoing, and very social. They are initiators, although they don't always finish what they start. Creative and popular, they love to be the center of attention and appear very self confident.

Type A
While outwardly calm, they have such high standards (perfectionists) that they tend to be balls of nerves on the inside. Type A's are the most artistic of the blood groups. They can be shy, are conscientious, trustworthy, and sensitive.

Type B
Goal oriented and strong minded, type B's will start a task and continue it until completed, and completed well. Type B's are the individualists of the blood group categories and find their own way in life.

Type AB
Type AB's are the split personalities of the blood groups. They can be both outgoing and shy, confident and timid. While responsible, too much responsibility will cause a problem. They are trustworthy and like to help others.