Moke Moke Taishou Dendou Musume Arisa

A strange android girl falls from the sky and crash-lands into Shinichirou's cafe, causing her to register him as her new master. Helping with chores isn't Arisa's niche, but she manages to fit in with his sister, Kotomi, until a new girl shows up looking for "Fire Bee". Through a series of sexual encounters, Arisa is found out to be the weapon "Fire Bee" Shinichirou's father was working on before he disappeared. Now the military is desperate to get her back at any cost. [Taken from ANN]