Nanako Shichigusa works in the Ogami Hospital under the employ of Dr. Kyoji Ogami. A buxom, hard working individual, Nanako, unfortunately, is not very smart, a lousy cook, and is about as graceful as a bull in a china shop! Any sort of mistake she makes usually ends up with her crying and pleading with Dr. Ogami not to make her one of his experiments, which he continually threatens to do with her. In the meantime, Dr. Ogami forces Nanako to perform exhausting physical training, which Nanako continually complains about and wishing that he would be a little kinder to her.
However, there is an underlying reason Dr. Ogami is doing this to her... Nanako is really a clone! In fact, Nanako is the third clone of a woman (who was also named Nanako) who has served the Ogami family since 1936. The original Nanako had died from a mysterious illness at age 20, but somehow with the technology of the time, a successful clone of the same woman was created, mainly in the hopes that a cure for the affliction could be found. But sadly, every clone that had been created has always died from the same illness at age 20.
The current Dr. Ogami was a boy of 8 when he became affected by the third Nanako. When she became ill, Ogami promised to become a doctor to try to find a cure for her. In the meantime, the third Nanako made a promise to stay with him no matter what happened. The young boy was terribly saddened when the third Nanako had died. He has carried on his family tradition when he created the current Nanako, which explains the almost-abusive training he has put her through.
And if Dr. Ogami's abuse wasn't enough, the other members of his organization often use Nanako in his absence to further his ambitions, often with Nanako in the middle of a dangerous situation, such as being mistaken for a cyborg when she was actually wearing a power suit, or being used as bait to lure rogue clones away from the lab. But somehow, Nanako perseveres, hoping someday that Dr. Ogami will treat her exactly how she hopes he treats her... with love and affection.
