Dii (ディー) is the primary antagonist of Utawarerumono. In fact, Dii was the original owner of the body he wears, and his true identity is now Uitsualnemetia's darker half. He believes in creating social progress by instigating wars to eliminate weak races and lead the people to greater heights through natural selection.
Dii is cold, calculating, and ruthless. He is a master of his own and uses other people willingly in order to achieve his goals. However, he is also bound by the rules as he explains that he and Hakuowlo were never meant to meet and fight because of their opposite natures. He also fulfills his end of the bargain honorably yet will willingly and mercilessly kill those that turn against him, like he did with Genjimaru. Because of Genjimaru's sacrifice, he spares Kuuya's life, though normally she would have served him in perpetuity as part of the pact that he made with her predecessor.
Dii was once a noble scholar of the Onkamiyamukai and Ulthury's mentor. Before the events of the series, he wandered inside the cave where Uitsualnemetia's soul was sealed. Having witnessed this, he attempted to leave the cave but it was then that the darker half was released and possessed his body, erasing whatever remained of his original self. This caused the earthquake around the land that wounded Aruruu and made Eruruu enter into a pact with Uitsualnemitea's good half, whom Dii, now the host of the darker half, became aware of.
Dii is revealed to have aligned with several nations in order to achieve his goals. The most notable being Shikeripechim and Kunnekamun. He told Niwe of Hakuowlo's true identity, thus making Shikeripechim declare war and provided the Abh-Kamu to Kunnekamun so as to fight against the countries that oppressed them and enter into a pact to be his people. He also deceived Orikakan with sorcery for Kucca Kecca to declare war on Tuskuru as per Niwe's plan. In the end, Dii lost the fight and, bound by the rules, intended to sleep until he awakens once more despite having an urge to fight Hakuowlo. Hakuowlo, however, decides to fight Dii and the two engage in their god forms. Dii nearly won but Hakuowlo decided to fuse the two halves of Uitsualnemetia together before sealing himself away so as to prevent interference from the god.
Genjimaru - Dii regarded Genjimaru as his only friend as he did not wish to lose him when he turned his blade against him. Even then, Dii held no emotion as he mercilessly killed him.
- In the visual novel, Ulthury reveals that Dii was once her teacher until his disappearance.