Loki to Omochabako no Oujo

"All androids must be disposed of by the person in charge of them." With people abiding by that one rule, science progressed rapidly for the sake of the happiness of everyone in the kingdom. Monica, a 10-year-old girl who is the queen of the kingdom, begins attending the school she first longed to go to, not knowing that every single one of her classmates is an android. Among her classmates who warmly welcomed her into the class (or rather, were programmed to do so) is an android named Loki. It looks like a young boy, and is the only one of her classmates to act coldly towards her. Loki has long had uncomfortable memories of humans, and therefore his distrust of them has been worsening. But unaware of that, Monica gradually becomes attracted to Loki... Thus begins the love story of a girl who, defying societal laws, had special feelings towards a robot. Source: Shogakukan