Isaac Dian (アイザック·ディアン Aizakku Dian) and Miria Harvent (ミリア·ハーヴェント Miria Hāvento) are the bumbling thief couple of Baccano!.
Issac and Miria are both very charismatic and effervescent, and "sprinkle happiness" upon anyone and everyone they meet without noticing. They have easily made friends with all sorts of people, Isaac even becoming friends with Ladd Russo while in prison. They also possess indomitable will as is suggested by their headstrong personalities, in addition to the fact that they have not changed between the 1930s and the 2000s.
Isaac used to live around San Francisco. However, he has a poor relationship with his family and avoids visiting them after his release from Alcatraz.
Miria almost died before the beginning of the series, for reasons still unclear. Isaac was able to make her smile when she thought she no longer could.
Isaac and Miria are a pair of clueless and eccentric partner-in-crime lovers who dress up in costumes and commit strange robberies, such as stealing candy and even the entrance door of a museum (so people "couldn't enter there anymore"). In 1930, the duo attempt to steal the entire fortune of Genoard (which they succeed) and Martillo Families. While attempting to steal from the latter, they unintentionally become immortal after mistaking the Grand Panacea for alcohol and drinking it at a celebration. The next year, after attempting gold mining in California without any luck, they board the Flying Pussyfoot and survive the bloody hijacking that occurs. Isaac is arrested for various thefts in 1934 and is imprisoned in Alcatraz, though he is released later that same year and reunites with Miria. After running out of money in 1935, Isaac and Miria make good on their promise to avoid crime and start working at Fred's hospital. The pair continue to live happily, finally realizing they are immortal 67 years later in 2001.
They both individually possess true immortality, meaning they cannot age, get sick, be injured, or die via conventional means. Immortality aside, they possess an endlessly large amount of good luck, having escaped numerous dangerous situations throughout the series without serious injury (taking them roughly 70 years to realize they were immortal).
Isaac has also demonstrated a few of times that he possesses incredible observational and deductive skills.
- They resemble the real-life thief duo Bonnie and Clyde to a more ridiculous extent, as Bonnie and Clyde's attempts at organized crime often went hilariously awry.
- Numerous publications in various media have been written on the subject of Isaac and Miria's characters. Most described them as the most entertaining characters and commented on how the series would not be the same without them. One reviewer felt that they are the protagonists of the series, which features an ensemble cast. They were awarded "Duo of the Year" in 2009 by Anime News Network.
- Isaac and Miria appear in the series' two drama CDs, where they survive the Flying Pussyfoot incident in 1931: Local Chapter and Express Chapter of The Grand Punk Railroad and hope to meet true revolutionaries in a small Mexican village when Firo Prochainezo witnesses the 53rd death of Pietro Gonzalez.
- They are playable characters in the video game and characters in the two-volume manga.
- They are used in the anime series to comment during the preview of the next episode; though their observations aren't usually very perceptive.
- The pair also made a brief appearance in an episode of the Durarara!! anime series, during which they are in modern-day Ikebukuro, Tokyo and attend the first meeting of the Dollars, an anonymous online gang. This seems to settle a debate over whether the worlds of Baccano! and Durarara!! are connected. They also appeared in the following OVA episode seperate from the main series, where they comment on the supposed UFOs seen shooting across the sky. These are actually yakuza members covered in paint that were thrown out a three story window by Heiwajima Shizuo.