Takuma Akutsu has been shunned since childhood over his permanently scary face, leaving him socially anxious and largely friendless, until nine Valkyrie sisters move into his house and upend his life completely. Sent down by Odin, the sisters need to grow emotionally close to a human partner to strengthen their combat power against the monsters threatening the world, and Takuma is the partner they have been assigned. The manga plays its harem premise for comedy and romance in equal measure.