Sumomo is a mobile persocom - which is the persocom equivalent of a laptop computer. She is programmed to be cute and tends to be quite hyperactive, for example her morning ‘wakey wakey exercises’.
At the beginning of the series, Shinbo uses Sumomo in an attempt to analyze Chi, and Sumomo is nearly broken in the process, requiring new main memory, and in the manga, a new video card as well. Once Kotoko joined Hideki, she quickly came to the conclusion that Sumomo was crazy, with her nonsensical ways. Sumomo’s password after being received by Hideki is Chobits (case sensitive) and ちょびっツ (case sensitive because of the katakana at the end)