Sasami is a hikikomori, who stays at home all day watching her onii-chan interact with others through her computer. On Valentine’s Day, after Sasami gives Kamiomi some chocolate, he unwittingly gives it to Yagami Tama, not knowing the meaning behind Valentine’s. After Tsurugi informs him about the tradition, Kamiomi finds himself wishing for chocolate from Sasami, and inadvertently turns the entire world into chocolate using his power as a god.

Sasami writes up a report explaining that the chocolate incident was the result of powerful gods appeasing to the wishes of Kamiomi, who unknowingly possesses the powers of the goddess Amaterasu. Meanwhile, many students are absent from school due to becoming engrossed in a fantasy social game. Intrigued by it, Kamiomi and the Yagami sisters borrow Sasami's spare computers to try it for themselves. Sasami, not wanting them to find something wrong with the game and shut it down, preventing her from playing it anymore, tries to interfere with their gaming to no avail and she inevitably reveals herself as a player while attempting to stop their tomfoolery. When a strange dark dragon suddenly appears, absorbing the spirits of all the players, everyone's minds end up getting sucked inside the game itself. The dragon is revealed to be something Sasami created three years ago when she once possessed the power of Amaterasu, which kept the game from being shut down.

In her report, Sasami explains how she was trained at the Tsukuyomi Shrine to inherit Amaterasu's power, which had been passed down from her family through incestuous means. She soon began to question her life after discovering the internet, eventually deciding to run away with Kamiomi. As she writes her report, Sasami discovers that a third arm has grown out of her chest, soon discovering it has a personality of its own, which tells him Kamiomi plans to return to the shrine in order to protect her from hunters who want Amaterasu's power. Struggling against the sunlight, Sasami comes across Tsurugi, who brings her to Tsukuyomi Shrine and reveals herself to be Amaterasu herself, who gave her power to Sasami's ancestors long ago. As Tama and Kagami arrive to attack the shrine, Tsurugi explains how she created them from parts of herself.

Sasami discovers a DVD containing a project by Kamiomi and the Yagami sisters involving them filming her in secret to record her progress. Putting the somewhat perverted nature of the DVD aside, Sasami can't recall doing any of the actions displayed in the video. As Sasami in the video winds up at a mini live concert, it turns out to be a trap set up by the Tsukuyomi Shrine, in which Sasami's father stabs her third arm and allegedly steals her power of Amaterasu. The video soon reaches its climax involving an all out battle between the shrine, the Yagami sisters and government forces trying to obtain an alien Tama came across. Tsurugi then explains that the DVD was made to explain things to Sasami, who is actually revealed to be the third arm, a sarcoma, who lost her memories and assumed she was Sasami and took her form. Sarcoma objects to being forced to return to Sasami's body, but Tsurugi takes away her power before she can object.

Feeling a bit isolated in school, Sasami gets Kagami to be friends with her in order to attract more friends. However, Kagami doesn't seem particularly interested since most of Sasami's suggested activities are unneccessary for her as a robot. Later that night, Sasami finds Kagami in a bloodied state, though she still refuses to be open with her. She becomes upset when she sees Kagami allegedly making some other friends, but cheers up after spending some time playing with Tama, who assures her that Kagami appreciates her friendship. Sasami soon comes to realise that the Myriad Gods are attacking Kagami out of jealousy for being chosen by Sasami to be her friend. After catching up to Kagami after she destroying all the gods inhabiting the school, she learns the girls she saw Kagami hang out were possessed by gods which she purified. Sasami apologises and asks Kagami to become her earnest friend, which she graciously accepts.