Reisen Udongein Reina (Short for Zero-series Number, or Reishiki Nanbaa)

Reisen Udongein Inaba (Short for One-series Number, or Ichishiki Nanbaa)

Reisen Udongein Futaba (Short for Two-series Number, or Futashiki Nanbaa)

The base model for creating the one-to-five series. There were a total of 1000 zero-series alive, but due to miscellaneous experiments and their transformation into the one-to-five series, only 100 models were left. Her default personality is completely pure and innocent. She is extremely curious, and is friendly with people. it wouldn't be a stretch to call her personality "child-like". The Mini-Udon who appeared in the "Silence of the Rabbits" belongs to the zero-series. Since she was raised in a cruel environment, she's always in a constant state of fear.

The mass production model derived from the growth of the zero-series. The protagonist Udonge from the main story is a one-series. Her attached ears allow her to hear things from far distances. A device is also installed to enable her to receive messages via electromagnetic waves. This function was originally meant for her to communicate with her comrades. but due to her solitary lifestyle they weren't of much use. These ears, however, are what that allowed Udonge to hear the voices of the original Eirin and the dead Tewi. "Inaba" is a abbreviation for the one-series number, and there's a serial number after that as well. Thus, the protagonist Udonge's real name is actually Reisen Udongein One-series Number #72.

Despite looking exactly like the Inabas, the two-series have greater spiritual and physical power, and thus perform better in battle.　The two-series are also created artificially on the moon. Nevertheless, the two-series are not as popular as the Inabas. This is because of the toughness of their meat, which render them unfit even as emergency rations. The lunar rabbits, after all, are food in additional to their normal roles as pets. "Udongein" is a famous brand of rabbits on the moon, and are considered a luxury food.