Character in Phantasy Star 4. Rika is a Numan, a genetically-engineered lifeform created by the computer known as Seed, which was located in the area called Birth Valley (not to be confused with Death Valley].
Rika is the latest in a series of similar lifeforms, beginning with Neifirst and Nei in Phantasy Star 2. By the time of the fourth Phantasy Star game, the high-tech civilization from PS2 had collapsed, and only a few facilities (such as Birth Valley) remained functioning. However, Seed remained functional long enough to create Rika, so I guess that's OK.
Rika was created only a year before she is first encountered in the game, thus making her technically only a year old. However, due to the force-growth biotechnology available in Birth Valley, Rika has the appearance of a girl in her late teens, thus making her without a doubt the sexiest one-year-old I have ever seen. Her appearance is improved by her cat ears (which make her technically a catgirl--at least in my book) and her outfit, which shows quite a bit of butt when she's viewed from behind. As the Phantasy Star combat system generally shows the characters from behind, the player is often treated to a nice view of her butt when she attacks.
Despite being both cute and sexy, and also being a catgirl, Rika has the additional advantage of being a genuinely nice person. Perhaps this is just because of her lack of experience in the world, but I doubt it. One of the best scenes where Rika's better nature comes through is when another major character dies. The main character, Chaz Ashley, is deeply saddened by this loss, and Rika reassures him in a scene that nearly made me cry, and it's hard for video games to do this (I laughed at the infamous Aeris-gets-impaled scene in Final Fantasy 7). It just goes to show you how good the Phantasy Star games are, and how great a character Rika is.