ハルカ

At first a robot shop's companion/guide robot that does nothing but introduces pet robots to customers, but later gets rebuilt by Mika and Kazuki with the self-thinking AI. She expresses many human emotion thanks to Kazuki’s base data and opts to be his imouto. Side note, Haruka’s got to be the most moe character in the heroine group. [Edited from a review by Warum]