A junior detective, 16 year old Yui Samidare is besmirched when a case she was called for ends with her waking up alone, most of the detectives with her dead. The lone survivor is a girl she met on the way there, a mysterious 13 year old named Kyouko Kirigiri.
Solving the case, Samidare and Kirigiri become friends. However, things are much more than they seem, and soon the two are dragged into a confrontation with the Committee of Salvation for Victims of Crime, an organization that wishes to grant salvation to those who have been wronged by crime itself.
These books contain examples of:
- Absurdly High-Stakes Game/Deadly Game: How the Duel Noirs play out, with a battle between detective and culprit and massive amounts of money on the line. Leaning more towards the former with Norman's Hotel, as the participants must take part in the "Right of Detective". It is revealed that there is indeed a serial killer loose in the auction house, and the detectives must figure out who it is. For every night that passes, someone will be killed off. If a detective wins the "Right of Detective", then they will be safe from the serial killer for the night. If you survive, then all of the money you have left will be yours.
- Anyone Can Die: Played with. While there are many deaths, most of them are of the murder victims, who, with the exception of the Norman's Hotel case, get very little characterization or are outright Posthumous Characters. Starting with Volume 3 (where the cast grows considerably), the deaths of characters the readers become familiar with are a lot less common.
- Big Bad: Mikado Shinsen, committee chairman, and Master of Disguise.
- Big Sister Instinct: A constant and important fact. Samidare as the series goes on becomes more and more protective of Kirigiri to the point of sacrificing herself if necessary, the result of failing to protect her own sister years ago. Indeed, the confrontation with Hitomoshi shows Samidare is willing to kill to protect Kirigiri.
- Breather Episode: After the despair and utter carnage of Volume 2, Volume 3 is much lighter. Much of it is less extreme than the previous book, the main characters' lives aren't in constant danger, there's a decent amount of light-hearted humor and very few characters actually die.
- Call-Back: Samidare's segment in Volume 4 begins in a way directly referencing the beginning of Volume 1, with her waking up from a long dream in Duel Noir after being knocked out.
- Chekhov's Gunman: In Volume 3, Kirigiri and Samidare go to a case in the latter half, wherein they meet four detectives, Hajiki Yaki, Korisu Kakitsubata, Sara Mizuiyama and Salvador Yadorigi Fukurou. None of them do much in the case except for Kakitsubata, who's the culprit, but come Vol 4 and the remaining three become allies.
- Continuity Nod:
- Despite not being featured, Hope's Peak is referred to quite a bit. Samidare even says she chose to not go there despite having the ability to because she wanted to be a detective.
- When it's revealed that the fourth 000 detective is a Master of Disguise, Kirigiri makes a reference to the SHSL Imposter.
- Tsurugi Hitomoshi, one of the hitmen encountered in Volume 3, is a Hope's Peak graduate.
- When confronting him about possibly being Shinsen Samidare is given by Jin a photo of him with a young Kirigiri. The description clearly labels it as the same photo that's in his office in the first game.
- Cool Big Sis: What Samidare is to Kirigiri, who even calls her "Onee-sama''.
- Dead All Along: Kirigiri's grandfather. No, not Fuhito, her maternal grandfather.
- Death of a Child: Suou and Shikon Kyuuren.
- Disappeared Dad: Jin Kirigiri has already left his daughter behind in favor of attending Hope's Peak Academy. Blame Fuhito refusing to let Kyouko see her dying mother.
- Enclosed Space: The Sirius Observatory is in the middle of a snowstorm, preventing outside interference.
- Even the Girls Want Her: Yui has received at least two love letters in her student career. Both while attending an all-girls school.
- Everybody Lives: With the exception of a few victims that never speak, no named characters die in Volume 3. Even Kakitsubata, who is seemingly killed after being outed as culprit, is revealed to be alive in the early parts of Volume 4.
- Fair-Play Whodunnit: One of the chief goals of the Committee is to create these with the Duel Noirs. Zigzagged somewhat on a meta level, however. The culprits are usually possible to pick out (if difficult), but the motives are more often than not never stated before The Reveal.
- Foregone Conclusion: Whatever happens, the series will end with the incident where Kirigiri's hands are burnt.
- Great Detective: Given the Detective Library is a massive database for all detectives, these show up a lot. The top, however, are the four who achieved 000 status, those being Gekkan Ryuuzouji, Johnny Arp, Rei Mikagami and an unknown fourth. Volume 2 reveals the fourth is the Big Bad and Master of Disguise Mikado Shinsen, with Ryuuzouji and Johnny working under him. Volume 3 subsequently reveals Lico to be Mikagami, though as it turns out, neither is his real name.
- Heroic Sacrifice: Samidare shields Kyoko from the elements until medical attention can arrive. When Kyoko later wakes up in the hospital, she learns Samidare didn't make it.
- Info Dump: A large amount is given by Jin at the start of Volume 4 concerning Fuhito, Shinsen, and their connection.
- Late-Arrival Spoiler:
- The series openly gives away the nature of Kirigiri's talent in the book. Not that it was hidden much anyway since Trigger Happy Havoc.
- The series also does this to itself. The cover of the fourth volume depicts three characters who were introduced in a case in the previous book, which had four suspects, one of whom was the culprit. While no direct visual image of the characters is shown there, enough information is given that the reader can match them to the fourth volume's cover, and the identity of the culprit (Korisu Kakitsubata) becomes obvious through exclusion.
- Locked Room Mystery: Twelve of 'em, courtesy of Ryuuzouji as a test for Samidare.
- Memento MacGuffin: Possibly, at the moment depending on how things go, but the rose in vitro Samidare gives to Kirigiri, later on becomes one of her favorite presents in Danganronpa: Trigger Happy Havoc.
- Mythology Gag: A certain door late in Volume 2 has an X on it that seems at first glance to be blood, but is actually pink paint, a clear reference to the Black Blood utilized by the games.
- "Not So Different" Remark: Ryuuzouji openly notes this to be the case with him and Samidare. Samidare isn't happy about it.
- Off with His Head!: The very first chapter involves three decapitations. All of them with their heads switched to a different corpse.
- Prequel: Needless to say this all takes place before the main cannon storyline kicks in.
- Red Baron: All four of the 000 Detectives have these:
- Gekkan Ryuuzouji - The Chair Detective
- Johnny Arp - The Executioner of Justice
- Rei Mikagami - Rei Mikagami, which is just a fake name used by Lico
- Mikado Shinsen - The Variationist
- The Reveal: Frequent:
- The end of Volume 2 reveals the chairman is Mikado Shinsen, the final 000 detective.
- In Volume 3, Lico is actually Rei Mikagami. The ending also heavily implies that Fuhito has been Dead All Along and has been impersonated by Shinsen for months now.
- Several are given in the first portion of Volume 4; the body Samidare found isn't of Fuhito, but of Kirigiri's maternal grandfather, Shinsen was Fuhito's former student who was set to be the heir to the Kirigiri family before Kyouko was born and the culprits in the Palace of Locked Rooms aren't killed, but taken safely to Ryuuzouji's castle, with him even paying debt.
- Ten Little Murder Victims: The motif of the of Norman's Hotel case, which involves ten people, including Kirigiri and Samidare, who get imprisoned and killed one by one each night. It seemingly ends as the culprit (Yozuru) is caught, only for Nanamura to turn traitor and kill nearly everyone, followed by him committing suicide.
- Two Aliases, One Character: Lico is Rei Mikagami.
- Two Lines, No Waiting: More like six. Volume 4 concerns six Detectives (including the main characters) who take on one case each, with the book covering all of them.
- Twisted Christmas: The incident at the Sirius Observatory takes place on December 22. Volume 2 begins at Christmas and concludes on New Years.
