Who sings the theme song for the anime Chobits?

That is a group called Nino/Round Table

Visit this website to download the opening http://gh.ffshrine.org/soundtracks/c and just scroll till you find Chobits Opening single. This is where I got it from.

The Talented Rie Tanaka (the same person who does the voice of Chii) sings the ending song Raison D'etre.

The opening song is

"Let me be with you" by Round Table ft. Nino

nino