Daisuke Niwa is a clumsy, block-headed, and wimpy middle school student who has few redeeming qualities. On his 14th birthday, he finally decides to confess his love to his longtime crush Risa Harada, but is rejected. In an unexpected turn of events, however, Daisuke finds himself transforming into Dark Mousy, the infamous phantom thief, whenever his mind is set on Risa. Though Daisuke is unaware of this strange heritage, his mother is certainly not: since before the boy was born, his mother had been planning for him to steal valuable works of art and let the name of the elusive art thief be known. With doubt and confusion constantly clouding his mind, Daisuke finds himself struggling in his relationships with classmates and family. And it is not long before Daisuke realizes that he is not the only one with a fated family legacy—his greatest adversary could be the one classmate he is most unwilling to fight.

After a routine raid, the rookie sky pirate Coud finds a most unusual cargo in his mates' cargo hold: Ren, an "Edel Reid", a race prized by humans for granting special combat power to their partners through "Reacting". He quickly discovers, however, that Ren is even more prized than he expected. The pirate ship is visited by three members of the Edel Reid Complete Protection Agency "Arc Aire", who try to purchase her. When Coud refuses, the ship is suddenly attacked by a mysterious force, and Coud's captain charges him with Ren's protection. (Source: ANN)

Thirteen years after their sudden disappearance, an alien race known as the Heterodyne resurface without warning. To combat the Heterodyne, three office workers from the 21st Century Security Corporation operate Dai-Guard - a giant robot no longer regarded as an oversized paperweight. Unfortunately, Dai-Guard is somewhat obsolete and in disrepair. It's a tough job, but salarymen can also save the world. (Source: ANN)