Shishimai Rinka was a high schooler who ran a small café named Lion House in place of her grandmother. She lived her life much like any other person her age, but one day, she was caught up in an explosion while returning home on the train alongside her friend, Hitsuji Naomi. In an attempt to save her friend's life, she shields her on instinct the moment the explosion goes off, losing her life in the process. However, before she knew it, she was back at Lion House, happily chatting with her friends as if nothing had happened in the first place.
"Good evening, my lovely little slaves to fate."
A few days later, she found herself in a strange world. Here she met Parca, an odd girl claiming to be a goddess. It turns out that she had somehow become a participant in Divine Selection, a ritual carried out over twelve weeks by twelve people, which allowed them to compete in order to undo their deaths. Yet, what shocked Rinka most of all, was the presence of her friend Mishima Miharu amongst the twelve.
In order to get through Divine Selection, one must eliminate others by gathering information regarding their name, cause of death and regret in the real world, then "electing" them.
This turn of events would lead to her learning about the truth behind her death, as well as her own personal regrets. She would also come to face the reality that Miharu was willing to throw her life away for her sake, as well as the extents to which the other participants would go to for the sake of living through to the end.
Far more experiences than she ever could have imagined awaited her now, but where will her resolve lead her once all is said and done...?
Fatal Twelve provides examples of the following:
- Amnesiac Hero: Rinka. She doesn't even recall the initial explanation of the Divine Selection game. She was so scrambled after experiencing her death and cannot recall her own cause of death or regret. This is due to Lethe's interference.
- Cast Full of Gay: Naomi and Miharu both have rather transparent crushes on Rinka. Miharu especially has strong feelings for her friend, revealed fairly early on, and Rinka can respond to her feelings later on. Even Odette reveals she "swings both ways" and implies Federico is similar to her.
- Cute Clumsy Girl: Naomi to a T. It's pointed out repeatedly that she's quite clumsy but she's also extremely sweet and endearing to people.
- Deadly Game: The setup of the "Divine Selection" follows this trope fairly well, with 12 participants being given 12 weeks to find out information on the other participants to eliminate them including: Their real name, their cause of death, and their biggest regret. Having all three pieces of information allows someone to elect another participant during one of the weekly votes.
- Downer Ending: Several, but the bleakest by far happens if you turn down Miharu's confession. Rinka doesn't have the strength to fight off Parca's possession and her consciousness is erased. Parca herself dies a month later in Rinka's body. This is the only ending in which all thirteen participants die.
- We Hardly Knew Ye: Numeral VI who is the first eliminated. though there is a brief flashback expanding on her character later on.
- Wham Line:
- "It's simple, really. I just so happen to be a survivor of a previous Divine Selection, as well as the goddess' vessel up until this round began."
- "The previous Divine Selection was held seventeen years ago, beginning July 23rd. Not only was I a participant, but your parents were, as well."
- "I've waited so long for this moment... For when I could finally claim you, Shishimai Rinka, as my vessel!"
- I somehow materialized a new card. XIII - Name - Dianna Harrison. A thirteenth numeral that shouldn't exist.
- Would Hurt a Child: Number XII. He has no qualms about threatening others to get information and aggressively wants to win, and some of the participants are rather young. He shows his colors rather early when he broke into a hospital and threatened to kill a bunch of newborns unless Number VIII/Keiko gave up all her information on the spot.