Rentaro Aihara is a character in Shadow at the Water's Edge.
Longtime friend and neighbor of the Shimizu's, Rentaro is also Miwako's boyfriend and the ryokan's handyman. He is into electronics, and bought a robotic cat, Suki, for Miwako and is working to create a robotic dog to go with it. His goofy and quirky personality sometimes annoys the Shimizus, but for the most part they get along. Rentaro can be annoying, but in an endearing way and is a friendly person. He dreams of one day moving to the city with Miwako, but she is too tied to the inn to move. Players can bump into Rentaro the first time they try to go into the male Ryokan's baths, and then he can be found working in the shed in the gardens.