Shunka Koito

She is the granddaughter of the founder of Chiko's school. She uses this to her advantage amongst her peers, so her initial reaction to Chiko's cleverness is hostility. She changes her tune, however, after finding out how much "fun" it is to be around Chiko and her Nijū-Mensō-related adventures. Her goal is to have as much fun as possible until she turns 16 and is of age for her arranged marriage. She often doesn't seem to care about how much trouble she causes, so long as she has fun. This means she has a habit of adding oil to the fire in dangerous situations because it would be more entertaining that way.

(Source: Wikipedia)