The bustling Tokyo shopping district of Akihabara has been infiltrated by "Synthisters," vampiric creatures who prey on the area's patrons, draining their social energy and will to live while blending in among the crowds. Nanashi, an otaku high-school student, is lured in and transformed into one of them by the shadowy Magaimono organization, but manages to escape with his mind intact. Aided by a mysterious girl and a band of local allies, he sets out to hunt the Synthisters down, the only way to defeat them being to tear off their clothes and expose them to sunlight, all while unraveling the conspiracy threatening his beloved Akihabara.