Dorii and Guraa are twin archers who serve under Oboro as part of Hakuoro's army. They're skilled enough to regularly command archer units, and they're basically inseparable—which makes sense, since telling them apart takes actual effort.
The main visual differences are pretty straightforward: Dorii has purple eyes and wears blue on the lower half, while Guraa sports blue eyes and red on the lower half. Beyond that, they're noticeably androgynous, so much so that even other characters in the story struggle to pin down their gender. Honestly, fans often treat them as a unit rather than individual characters, since they're always together anyway.
Content compiled by AnimeList.moe from publicly available sources.
