Konnyaku Yunna, a girl who find herself unknowingly in trouble many times, witnesses a drug smuggling deal and later gets chloroformed for her trouble. Luckily the titular ninja come and save the day, starting the series.
Source: mangafox.com
Fuyuki goes out to buy groceries. When taking a break a cute girl falls right out of the sky in front of him. He then takes her home...
Source: mangafox.com
Miki, after witnessing a fight between Abdul and his uncle, get chloroformed by one of said uncle's henchmen. Later she is awake and about to be sold in a women auction, until Abdul come to her rescue.
Source: anymanga.com