In Tokyo in the year 2020, Sahashi Minato has failed the college entrance exam twice, is awkward around women, and unemployed. One day, Minato meets a girl named Musubi, who literally falls from the sky.

Minato soon learns that she is one of the Sekirei and he is her Ashikabi, a human with special genes make it possible to form a contract with Sekirei. This binds the Sekirei to him and allows them to use their full power in the Sekirei Plan, a dangerous and deadly competition organised by Minaka Hiroto, chairman and founder of the mysterious and powerful MBI Corporation. Minato finds out that being the partner of a beautiful girl is not all fun and games, especially when it turns out that an Ashikabi can have more than one Sekirei partner — and that is where the real trouble starts.

[Source: AniDB]