Umi's a rather interesting character. She can be really funny sometimes while extremely serious at other times. She's your typical rich-and-great-looking-Japanese-high-school-girl. She looks elegant on the outside, but more like a kid inside. And because of this, some people argue that of the three knights, she's the most realistic one.
Umi doesn't change much in the second season, but the way her fans saw her sure did. There's a continuous argument going on about should Umi end up with Ascot or Clef with hints along the second season. If you want to know our take on it, head over to the FAQ. Personally, I don't really care who she ends up with, I just know she looks pretty :P
Facts about Umi
Mokona is Umi's enemy of life.
Umi likes picking on Fuu about Ferio.
"I like you too Ascot! Along with Caldina, Larfarga and Ferio!" - Umi, second season.
Umi's calls Alcyone "oba-san" (means old woman), which pisses her off.