Based on a seinen manga by Gokurakuin Sakurako, serialised in Young Gangan.

Sahashi Minato is very intelligent, yet due to his inability to cope with pressure has failed the college entrance exam twice. As a result he has been branded an idiot and loser by many. One day after talking to his yet again disappointed mother he comes into contact with a girl named Musubi, who was under attack. The girl runs but takes him with her and soon finds that Minato, while unknown to him, is an Ashikabi, one of the mysterious set of masters that have the genetic trait that can become partners with some of the 108 cute girls, buxom women, and bishoujo called Sekirei. Only by means of such a partnership can the Sekirei use the full potential of their powers to win in the competition held by the ominous MBI corporation.