High school student Sora Kashiwagi is accustomed to receiving bizarre presents from his father, who is on an expedition around the world. Unfortunately, these gifts have been nothing but nightmares. As a result, when his father sends him a huge package from Egypt, Sora prepares himself for the worst, only to be greeted by Mii-kun—a cute, pint-sized mummy! While initially wary, Sora soon learns that Mii-kun is harmless, a delicate creature yearning for attention. Throughout their amusing day-to-day lives, the unlikely pair meet other people with unique pets, while also strengthening their bond together. Although keeping a pet is a difficult task, Sora is set on caring for the lovable Mii-kun.

In a thoughtless blunder, God accidentally strikes down Touya Mochizuki with a stray bolt of lightning! As an apology, God offers him one wish and the chance to live again in a magical fantasy world. Touya happily accepts the offer and, for his one wish, asks only to keep his smartphone with him as he begins his journey into this mysterious world. Starting over in this new world, Touya finds it is filled with magic—which he has an affinity for—and cute girls vying for his attention. These girls—the twins Linze and Elze Silhoueska, Yumina Urnea Belfast, Leen, and Yae Kokonoe—provide Touya with no end of romantic frustrations, but also companionship as he discovers the secrets of this new world.

The urban legend of the 4:44 ritual consists of using a radio player to produce frequencies in front of the Akeyuki Sacred Tree at exactly 4:44, transporting people to a different dimension. When Asuka Tsuchimiya and her friends—Nana Nanase, Mia Silverstone, Yuu Tounaka, and Chloe Morisu—decide to perform this ritual as an activity of the Crystal Radio Research Club, they are shocked when the ritual works. The five travel to a parallel world, known as a fragment, where they meet an unsettlingly familiar girl—Asuka's parallel-world self. This Asuka is dubbed as Seriouska due to her serious attitude and capability to fight. Seriouska tells them about the great danger that faces all the parallel worlds, the Twilight. As it strips the parallel worlds of all of its possibilities, Seriouska seeks the death of the man behind the Twilight, the Twilight King, to stop his onslaught over the multiverse. Akanesasu Shoujo follows the five girls as they learn to accept their true selves, all the while searching for the Twilight King. However, the solution to the invasive Twilight might be closer than they think.

The story follows the school life of the three girls, Yuzuko, Yukari, and Yui, who join their high school's Data Processing Club. The odd friendship between the three make for wacky humor in even the most mundane of events.