Ueda's persocom. Ueda originally bought her because he was not so good with math.
As time passed he fell in love with her and decided to marry her. However soon after marriage she started to forget customer orders, and even forgot Mr. Ueda's name. It was later discovered to be cause by a hard disk failure. He could not bring himself to have her repaired because her memories might be lost completely in the process of transferring them to a new hard drive, and he felt she would not be the same person if this happened.
One night while walking with his persocom, Ueda, lost in thought, walked into the middle of the street, unaware of an oncoming truck. In a final moment of clarity, his persocom pushed him out of the way and was herself run over. Her last word to Ueda was "Konnichiwa"; the default greeting for a newly activated persocom with no memories.