From MangaHelpers:
Nanako is an athletic and free-spirited girl that excels in every sport she does. Many of the sports groups at her school request her assistance at important matches. Where she excels the most is when she finds herself in a bind that will strip her of her clothes, while Keisuke Kawara ogles. You would think Kawara is the luckiest boy alive until you see the end result of Nanako's "accidents." [DrCoke]
Nanako is an athletic and carefree girl. But she is too carefree, and she often ends up in embarrassing situations, most of which are witnessed by her classmate Kawara, who, like any normal guy, enjoys it very much.