Ofuro no Tomodachi Furo Buddy

From MangaHelpers:
22-year-old Mabuchi Nobuko is the often-childish boss of a toy company. She decides that bath toys should be developed for adults, which results in a new line of bath buddies. Nobuko tests out these new toys, as does her little brother Sakuno. The prototype units are a boy doll named Yuzu and a girl doll named Roze, and they work to make bathtime as childishly fun as possible.