Suffering from a traumatic event, teenager Rowan is whisked away from home and taken to her estranged aunt’s oceanside home indefinitely. Racked with guilt and unable to enjoy a normal summer, she drowns out the noise with increasingly bizarre, violent internet content. Soon, Rowan comes across videos of a missing woman known only as Fish Tooth, who she believes is calling out through the screen for help. Despite a budding relationship with her camgirl neighbor, Alex, Rowan’s obsession with Fish Tooth will lead her to something sinister lurking at the bottom of this twisted internet rabbit hole, and uncover what lies her own family has been hiding…

【本片翻译由澄空字幕组提供】失去姐姐而过著懒散生活的男主角・皋月驱和他的青梅竹马水奈瀬ゆか，突然一同被卷入一个染红的世界。然而，与另外4位来自相同世界少年少女一同被卷入到这个事件中，并且已打倒黑骑士们为目的。为了生存下去，并结束“赤之夜，他们与黑骑士们的战斗也就此开始