They are the 22 dimensional stewards working for Tokimi and the other Choushin.
D4 rules over 4-dimensional space, whereas D11 rules over 11-dimensional space, and so onwards.
Powers and Stats
Name: The Ds
Origin: Tenchi Muyo!
Gender: Varies with Member
Age: Likely beyond the concept of time
Members: D-1, D-2, D-3, D-4, D-5, D-6, D-7, D-8, D-9, D-10, D-11, D-12, D-13, D-14, D-15, D-16, D-17, D-18, D-19, D-20, D-21, D-22 (Each has nearly absolute authority over its respective dimensional space.)
Classification: Higher-dimensional entities
Attack Potency: Hyperverse level (22-dimensional entities)
Lifting Strength: Immeasurable
Striking Strength: Hyperversal
Durability: Hyperverse level
Standard Equipment: None