The second to lowest class. Like E class demons, they usually aren't very smart (with a few exceptions) or exceptionally powerful; but their strength and endurance is super-human compared to an average person. However, compared to most demons they are very weak. According to Koenma, Hiei was a high D class when he first fought Yusuke.
The second weakest class of demons, they are very common in the beginning of the series and become less important as more powerful classes are introduced. Most spiritually aware humans are at least D-class aside from those who have gained enough spiritual training.
From what has been seen from the series, D-class are almost always monstrous, standing several feet above human size, although some higher ranked ones of this class are much smaller and more humanoid. The generic personality of this class is overconfidence, sadism (laughing at other's emotional pain rather than physical pain of the higher classes of demons) , idiocy, dishonor and high view of themselves. However, when faced with defeat, they become desperate, even fearful for their lives. The powers of this class are more physical based, so that they can dominate with overwhelming strength, thinking little of strategy. This isn't always the case as both Kurama and Hiei, two former A-class demons, are forced into this rank after losing power due to certain events, and eventually, they regain not only their former rank, but move up to S-class. Thus the system is not set, and demons can move up ranks as they gain power and experience. D class have more control over their instincts than E class and show more prudence in daily life as most D class demons will try to blend in with human society. However they also tend to be even more arrogant than E class because they are amongst the strongest on earth (though still very weak in the demon world). Powerwise D class are superhuman but the level of destruction they can cause is usually no more than simple property damage. (destroying a car, breaking a tree, smashing a wall, etc.) A single D class demon is strong enough to kill a platoon of well trained and well armed soldiers.
- Bakken and Genbu are the only two D-Class demons that display a use of a technique, and both are deceased, killed by Yusuke and Kurama respectively. Bakken could be presumably be alive as it was stated by Doctor that Yusuke had never killed anyone.
- It can be assumed since D class are fairly weak in comparison to most of the population of the demon world that many, if given the chance, migrate to the human world where they can live in relative safety. Most of the demons shown to live on earth appear to be D class.