Despair Disease is a motive introduced in the third chapter of Danganronpa 2: Goodbye Despair.
In truth, it's a fictional disease that exists only in the Neo World Program's virtual version of the island. "The insects" appear to be just a story made up by Monokuma, who can cure and supposedly inflict the disease in a flash.
According to Monokuma, the Despair Disease is a "Reaaaally annoying disease where you get a high fever, along with various other symptoms that are full of despair!".
People who catch the Despair Disease will get a high fever. They turn very weak and need lots of rest, but they're still capable of moving and walking around (depending on the symptoms, they may even be very energetic and eager to move despite their weakened state). Nagito Komaeda's symptoms are far worse, as he constantly loses consciousness and stays unconscious for most of the time, foams at mouth, is incapable of moving and is even close at dying - it's implied that this is due to the fact that he was already terminally ill before catching the Despair Disease.
The most notable symptom is a significant change in the individual's personality, which lasts until the person is cured. The symptoms of the victims are the opposite of their normal personalities and thus different based on the individual. For example, Nagito was afflicted by the Liar Disease, Akane Owari had the Coward Disease, and Ibuki Mioda had the Gullible Disease.
Due to the fever and personality change, most of the ill people appear to be in a groggy, fuzzy-headed state. Most likely, they don't remember everything that happened while they were sick. Mikan Tsumiki, on the other hand, is capable of clear, detailed planning while suffering from the Remembering Disease.
The disease is highly contagious and can get passed from person to person easily, just like the common cold.
Chapter 3 - Trapped by the Ocean Scent
The students meet up at the restaurant as instructed by Monokuma. Hajime Hinata found Akane who was unexpectedly crying and mourning after Nekomaru Nidai, who was injured by Monokuma, in a very emotional manner. Eventually, Hajime notices that Nagito is acting strange as well, such as stating that Fuyuhiko Kuzuryu was cloned after his injury and a transfer student would replace Nekomaru who couldn't be saved. He even lied to Hiyoko Saionji that he saw Mahiru Koizumi being alive at the movie theater.
Eventually, when Ibuki turns up, everyone notices that she is acting unusually casual. Moments later, Monokuma explains that Ibuki, Akane, and Nagito have caught the Despair disease. He also admits that he placed them overnight.
None of the students know how to cure the disease, but Mikan takes care of the three. Whilst caring for the others, Mikan catches the despair disease herself, causing her to remember "her beloved". After Ibuki and Hiyoko are murdered, Monokuma quickly heals the victims and brings them to investigate the murder. Although everyone is cured of their symptoms, Mikan continues to remember "her beloved".
List of Victims
- Nagito Komaeda: Infected by the Liar Disease, which caused him to compulsively tell outlandish lies.
- Akane Owari: Infected by the Coward Disease, which turned her into an emotional wreck who was constantly afraid, crying, and apologizing.
- Ibuki Mioda: Infected by the Gullible Disease, which caused her to believe everything she was told. It also made her inappropriately casual, although this may be a combination of the disease's effects and her own upbeat personality.
- Mikan Tsumiki: Infected by the Remembering Disease, which caused her to regain her memories of being part of Ultimate Despair.