Rena

At first Rena (Cf-3357L-JPA) appears to be a lost 9-year-old girl, discovered by Kazuya and May. However, she is another cyberdoll sent by Cyberdyne to recover May. Rena decides that she likes Kazuya and Ikariya and does not return with May to Cyberdyne, instead she moves in with Kasumi. In the Japanese audio, she is referred to by everyone, including herself, exclusively as "Rena-chan."

(Source: Wikipedia)