Hitomi Tsukishiro's monochrome world is devoid of emotion and sentiment, despite the kaleidoscope wonder engrained in everyday life. Hitomi's grandmother Kohaku weaves a magic, for which she has been harnessing the moon's light for 60 years, to send Hitomi back in time to the year 2018, when Kohaku was in high school, on a night as black and white as any other, amidst the fireworks spreading across the sky. Hitomi's mission isn't obvious, but her grandmother tells her that she'll figure it out once she arrives. Hitomi finds herself in the room of stoic artist Yuito Aoi after a trip through time aboard a train operated by a strange yellow creature, and his pictures flood her world with color. Why is Hitomi there, and what is her purpose?