The 4:44 ritual is said to allow anyone who broadcasts specific frequencies from the Akeyuki Sacred Tree using a radio at that exact time to travel to another dimension. Asuka Tsuchimiya and her friends Nana Nanase, Mia Silverstone, Yuu Tounaka, and Chloe Morisu put this legend to the test as part of their Crystal Radio Research Club activities. To their surprise, the ritual works, and they end up in a parallel world known as a fragment. There, they encounter a girl who looks almost exactly like Asuka but is serious and strong—she calls herself Seriouska. She warns them about a dangerous force called the Twilight, which is consuming all parallel worlds by erasing their unique possibilities. Her goal is to defeat the Twilight King, the one responsible for spreading the Twilight across the multiverse. The story follows the five girls as they discover their true selves and search for the Twilight King. However, the key to stopping the advancing Twilight may be closer to them than they realize.