He is a robot that worked as a maid at Yusaku's house.

Built and programmed by Yusaku, Roboppy is very loyal and respectful to him. Yusaku cares and visibly has a fondness for his house cleaning robot, as he warmly smiled and petted Roboppy affectionately as seen in his flashbacks. Roboppy does describe Yusaku as being "a little cold hearted."