When Hikari was little, she and her father liked to watch pro wrestling, and she became very good at it. She was the pride of her family until one day she was introduced to Kei, the son of her father's friend. He instantly defeated her in wrestling, and started what would become Hikari's major ambition to one day beat him. To do this she enrolled in Kei's school, an ultra-elite school that costs her father a lot of money. This unusual school creates classes according to grades, and the top seven students become members of the Special A. They have their own building, and can optionally attend class. Hikari is usually the only one who does so, since she desperately wants to beat Kei in the test scores. The members of the Special A have been close friends since their first year.

[Source: AniDB]