Tragically perishing from overwork, a young Japanese woman is reborn as Dahliya Rossetti, daughter of a newly entitled baron. Her father, Carlo, is a beloved magic artificer, a maker of magical tools. Inspired by him, Dahliya uses her memories from her previous life to create practical inventions and become a magic artificer like Carlo. A few years later, the now adult Dahliya has made a name for herself and has gotten engaged to her father's apprentice. However, her life takes a turn for the worse when Carlo suddenly passes away and her fiancé leaves her for another woman not long after. Although having to fend for herself, Dahliya is not quite ready to give up on her dream of becoming a master artificer yet. She may be a single woman but, with the help from old and new allies, she is prepared to overcome any obstacle in her way.

After waking up in her room on Christmas Eve, high school student Ryouka Tsurumi makes a series of chilling discoveries. Her mother informs her that her mansion has been evacuated and the area placed on lockdown due to the presence of an unknown and dangerous entity named X. The only other person left in the building is Shuuhei Murosaka, Ryouka's childhood friend. To add to the horror, Ryouka learns that X can brainwash people for its gruesome goal: feeding itself of human blood to reproduce. However, Shuuhei comes to Ryouka's rescue and manages to save her from one of X's brutal attacks. As the two friends try to escape from the lockdown area, they are captured by hypnotized humans and subsequently devoured by the giant beast. But for Ryouka, the nightmare has just started: she wakes up for the second time in her room, only to find out that a different X is now threatening her life. Realizing that she is stuck in a time loop, Ryouka decides to team up with Shuuhei to find a safe future away from the threat of X.