For some reason, Sasami decides to seclude herself in her room over spring break, using her power to create a barrier that seals off her home from the outside world. Feeling this will have implications on the world if it goes on, Kagami, Tama and Kamiomi attempt to break their way inside the barrier, where they are met by Sasami's resistance. After struggling a bit, they are soon joined by Tsurugi, returned from the underworld, who instructs Tama to eat her way into the barrier and bust into Sasami's bedroom. There, they discover the reason for Sasami's seclusion: she had suddenly gotten fat overnight. To explain what happened, Tsurugi shows Sasami the past through the perspective of Juju, learning of a side of her that she never showed to Sasami. Just then, an assassin from the evil society Arahabaki named Tamamo-no-Mae appears with a stone golem, capturing the young Sasami and speaking of changing the future.
The Japanese call them hikikomori-people who've become so withdrawn socially that they refuse to leave their homes for weeks and even months at a time. For Sasami Tsukuyomi, who's attempting to pass her first year of high school despite being a shut in, it's more than just a word. Fortunately though, she lives with her older brother Kamiomi, who just happens to be a teacher at the school Sasami is supposed to attend. Not to mention, her "Brother Surveillance Tool" which lets her view the outside world via her computer and will, theoretically, allow her to readjust to interfacing with people again. What it mainly does, however, is let her view her brother's interactions with the three very odd Yagami sisters, who inexplicably seem to have had their ages reversed and have various types of "interest" in Kamiomi. And then things start to get really weird... Magical powers? Everything turning into chocolate? Is life via the web warping Sasami's brain, or is it the universe that's going ...
