It is well known that Souseki changed his writing style for each work. However, the intention and method with which he changed it have not been disclosed yet. The purpose of this paper is to clarify the way he changed his style with “Mon” as one example. In this paper, we focus on the relationship between depiction speed and style, and conclude that the style was changed by manipulating the description speed. Sometimes, using antithesis makes the reader feel the description more quickly. Sometimes, adding an unnecessary insertion phrase slows down the flow of the description. In some cases, increasing the number of words by using a periphrasis or duplicating expression makes the speed of description slow down drastically. The number of words and the speed of description are closely related to the expression effect, and when the depiction speed is high, the impression on the reader is light, and as the number of words increases, the impression of the description becomes heavier. Souseki skillfully exploited these effects, which compensate for his way of avoiding the direct expression of emotions. Some of the styles that he tried in “Mon” were those that had not been found in previous works. It contained some styles that were used in later works such as “Kokoro”, as well as some styles that were not used again thereafter. “Mon” was a work in which he experimented with various styles, and in writing this work, he seems to have grasped the techniques of manipulating style.