After winning an intergalactic competition for possessing the purest heart, Yuna Kagurazaka, a 16-year-old girl who is endearing but accident-prone, transforms into the Savior of Light - a superheroic and magical girl that pilots the mecha El Line to maintain universal harmony. Things take an unexpected turn when Yuna is falsely accused of obliterating a metropolis with El Line, and she is captured and imprisoned by Misaki Ichijouin - a special Galaxy Alliance agent. Though Misaki initially falls for the ruse, she soon realizes the deception and bands together with Yuna's comrades to liberate her and safeguard the galaxy from an impending malevolent entity's resurgence.