Be warned that all spoilers are unmarked. It's virtually impossible to list tropes for this roleplay and its characters without spoiling everything or creating Self Fulfilling Spoilers.
Introduced in DA1. The current headmaster of Hope's Peak Academy, he assisted with the Developmental Analysis Program, or DA Project. As of Black/White, he has become a member of The Collective, and after the ending of those games, he escaped to Arcadia with the students of Alpha/Omega in tow. Yasuda tends to work with many of the Masterminds of the games, although whether or not they remain loyal to him is another question.
- The Bad Guy Wins: In the first game. He's more than pleased with the results of the DA Project, and mentions in passing the idea of future projects along the same lines.
- Cross-Popping Veins: A pair of these appear hidden in his hair several times, first when he berates the survivors for signing the liability waivers without thinking about what kind of projects require them.
- Dissonant Serenity: He's almost always smiling.
- Expy: Basically a human Monobear. Justified by how Monobear was based on him.
- Faux Affably Evil: He's all smiles while explaining the horrors he helped create, or when directly threatening the students to stop their plans.
- For Science!: The entire reason behind the Developmental Analysis was just to gather and measure results on how students with such hopeful talents could adapt to being placed in the ultimate "stressful situation".
- Karma Houdini: Erases the survivors' memories of the second phase of the DA Project and makes it appear that the Central Wing was hit by a terrorist bombing, using that to excuse all the deaths. This lets him get away with the DA Project, and sets up for further horrors down the road, such as the testing in the second games that quickly goes awry. After the chaotic ending of the second game, he's sent away to a Collective shelter with yet another class of students. He's imprisoned before he can carry out any testing on them, but he's freed from his jail during the ending; it's unclear what his standing with the Collective is after that, however.
- The Man Behind the Man: For the first game. As the Headmaster, he helped set up the DA Project, and tellingly shares many of Monobear's mannerisms. While Monobear was a fully autonomous AI, Yasuda could take control at any time.
- Pet the Dog: Following the first game, he paints his erasure of the four survivors' memories as this — he's giving them a chance to live without remembering the horrors they endured. In reality, however, it's all part of his plot to get away with his crimes scott-free.
- Red and Black and Evil All Over: In the first game, he looks like a Man of Wealth and Taste in his black suit with its crisp red tie and the neatly folded red hankerchief in his breast pocket.
- "Uh-Oh" Eyes: Has solid black irises that perfectly blend in with his pupils.
Introduced in DA2. A secret, shadowy organization that has been running society from behind the scenes. Claim to be working towards a peaceful future without any conflict at any cost.
- Brain Upload: One of the things they research are Augmentation Chips, which comes up in the second and third games. It accounts for the continued existence of the dead students. They were supposed to record patient data (which includes memories, personality, and appearance) to a Backup System Grid, but in Black/White, the BSG had the unintended side-effect of giving the data sapience in the event that the patient died.
- Body Backup Drive: One of the things they research, which comes up in the second and third games, and is offered to the survivors in the ending as a possible way to bring back the dead.
- The Augmentation Chips in Black/White were supposed to record patient data (which includes memories, personality, and appearance) to a Backup System Grid, but the BSG had the unintended side-effect of giving the data sapience in the event that the patient died. During the ending, it was teased that this data could be inserted into bodies to effectively revive that person; it nearly happened with Black's Mastermind during the escape, but another student killed her clone's body instead of awakening it. The students of both games escape with the data, although it's not known if they ever find appropriate bodies.
- The ankle bracelets in Alpha/Omega/Epsilon were an intentional way to preserve that data and put it into a cloned body, with the sapient data staying safe in Elysium. An alternative is inserting the data into a humanoid robot, something that Alpha's Mastermind is forced to use; he then mentions that there are numerous other robot bodies in Gaia and suggests that others upload their data into them, although no one accepts his advice. Several students instead stay in Gaia for three months to clone human bodies for the deceased, allowing the whole class to walk out alive.
- Out-Gambitted: Both Black and White survivors chose to preserve their dead friends' data, the evidence against the Collective, and the Collective's research. The Collective was expecting Black to do this and is actually okay with it, since they feel their research is worth it. But the White game was run by rebel organization Doctrina Artifice, and since White chose not to screw DA over by destroying the evidence, Doctrina Artifice was able to broadcast the Collective's misdeeds to the world.
- Powered by a Forsaken Child: The sixty students in Black/White were signed over to them for their own experiments. Invoked by the Doctrina Artifice when they revealed these experiments to the world. Later, it's suspected that they planned to do this to the students of Alpha/Omega, who were reliant on the Collective for shelter and safety after the fallout from Doctrina Artifice's broadcast.
- Well-Intentioned Extremist: Supposedly out to guide the world to a peaceful new age by controlling it through whatever means necessary.
Introduced in DA2. A resistance group working to expose The Collective's crimes against humanity, and perfectly willing to commit horrible crimes in the process.
- The Bad Guy Wins: It turns out that the Doubt Academy Black and White games were a power struggle between the Collective, which is currently running the world, and Doctrina Artifice, a just as nasty rebel organization hoping to bring the Collective down. Since both games' survivors chose to save their friends' data as well as the evidence of what the Collective did, Doctrina Artifice wins the power struggle since it gets to broadcast this evidence to the world to bring the Collective down.
- Do Not Adjust Your Set: Part of the climax of Black/White. Hijacking the airwaves, they broadcast images from the two mutual killing games, blaming all the deaths on The Collective.
- Faceless Goons: The member who appears in the broadcast at the end of Black/White is wearing a Monobear mask.
- The Revolution Will Not Be Civilized: They kicked off the Game of Mutual Killing in Bright Side Spa, framing it as solely the Collective's doing and executing their spy to add just one more death. And as noble as their goals may have otherwise been, after DA3 it's clear that their broadcast has caused nationwide if not global panic, turning Japan into a land with no stable government, with the citizens distrustful of everyone around them, regardless of their affiliations.
- Well-Intentioned Extremist: Out to ensure The Collective is exposed and falls at any cost.
- You Have Outlived Your Usefulness: In White, after their Mastermind Mole is exposed, they proceed to execute him. The Monobear who breaks this news to the mastermind gloats that his death will be another symbol of The Collective's crimes against humanity.
Introduced in DA3. A group of old friends, consisting of Takeshi Nara (a Collective researcher), Etsuo Yamaguchi, Ataru Kato, and Mahiru Ueda. Takeshi survives the Masterminds' takeover of Arcadia and leaves a distress message to his friends before being imprisoned; it doesn't pay off until the Game of Mutual Killing ends, however.
- Eyes Always Shut: Mahiru, whose eyes are almost always closed aside from a few scenes: First, in the large image introducing Takeshi's friends. After that, they open when she speaks of particularly grave subjects, or when she's demanding that her friends stop fighting and arguing.
- Fun with Acronyms: The initials of their first names (Takeshi, Etsuo, Ataru, Mahiru) make up the word "team".
- One Steve Limit: Averted with Etsuo, who has the same first name as Etsuo Takahashi from Black. However, that student was known almost exclusively by his nickname King. Later, the surname Yamaguchi appears again with Rot's Keita Yamaguchi, while Ataru's surname Kato appears with Noriaki Kato (aka T△K△).
- Reluctant Mad Scientist: Takeshi genuinely wants to help people with the technology he was working on, especially the projects that could help those terminally ill or mortally wounded have another chance at life. He was absolutely disgusted once he realized that the Collective was putting high schoolers in danger, getting most of them killed, and readily turns against his former employers when given the opportunity. For what it's worth, it's not stated if anything he worked on was directly used to make anyone suffer.
- Sole Survivor: Takeshi was working with five other researchers, but they were killed during the Masterminds' coup; it's implied the only reason he was spared was because Gorou got to him before Yuuto did. This also means that Takeshi is the only person alive who knows how to operate the cloning technology, and thus he must turn down his friends' offer of help if the dead students are to be saved.
- Tsundere: Ataru. An e-mail pieced together in the Isolation Ward shows them yelling at Takeshi and making threats on his life, and in person they're harsh to both Takeshi and the students. However, this anger stems from a concern over people's safety, and after the timeskip they offer their aid to any students who don't have a home to go to.
- You Gotta Have Blue Hair: Mahiru's hair is a greenish-blue.