1. A message-browsing system for providing a browsing service for browsing messages exchanged through a post and a response to the post, among multiple users, the system comprising: a memory configured to store one or more instructions; and a processor configured to execute the one or more instructions to: access an image storage configured to store user images to be displayed on a screen, each user image corresponding to respective ones of the multiple users; access a motion storage configured to store pieces of motion information defining motions of the user images, in association with types of feelings or forms of posts; access a keyword storage configured to store keywords according to the types of the feelings; retrieve a post including a sentence posted by a user, in a case in which the post by the user is a first form, among the forms of posts: determine whether or not any of the types of the feelings is identified within the sentence of the post by analyzing whether the sentence includes any of the keywords stored in the keyword storage; select, in response to and based on a type of feeling, among the types of feelings, identified within the sentence of the post, one of the pieces of motion information indicating a manner in which a user image of the user moves corresponding to the type of feeling identified within the sentence of the post; select, in response to determining that the sentence of the post does include any of the keywords corresponding to the types of feelings after analyzing the sentence posted by the user, one of the pieces of motion information indicating a manner in which the user image of the user moves depicting the first form of post; and set a motion of the user image corresponding to the user who has contributed the post based on the selected piece of motion information.