At “The International Congress on Love & Sex with Robots,” love and sex issues related to robots have been discussed. This discussion of robots has applications in nursing care and other. Love and sex are also important themes for narratives. We develop a system to generate stories, and consider a robot that tells stories as one of the applications of story generation. The purpose is to present a prototyping system that generates a new narrative expression based on the theme of “love and sex” by exchanging the concept of character in the input narrative expression with a new concept using our noun concept dictionary. We call the method of collecting nouns based on a certain theme and embedding them in a story to give the story a certain atmosphere “colouring.” This paper is to develop a prototype of a system that uses “colouring” to give a certain atmosphere to a story. We create a prototype and study the issues of the system. In the future, this prototype will serve as a stepping stone to a system that generates narratives based on specific themes. Eventually, we will study the use of robotic interactive psychotherapy, in which the robot converses with humans.