In this paper, we will analyze the main box office factors of modern fantasy web novels. Regression, inscription, and reincarnation motifs are narrative structures frequently applied in modern fantasy web novels and are the biggest features that distinguish them from pure literature. In addition, the attractive protagonist is one of the core elements of the web novel and determines the overall flow of the work, and the reader feels strong surrogate satisfaction with the protagonist's narrative, role, and growth process. Therefore, this study comprehensively explores the unique narrative structure and protagonist characters found in modern fantasy web novels and analyzes their influence on their works. Based on the literature survey, a case study was conducted to promote an in-depth understanding of specific cases. The subject of this paper, “The Youngest Son of a Chaebol House,” is a modern fantasy web novel by Sankyung author who applies the regression code, which is the box office formula of web novels, and sets the modern and contemporary history of Korea, and has gained explosive popularity in Munpia from the beginning of publication, and refers to a chart arranged in the order of the highest number of views per day (24 hours) from 1st to 103rd (PC) and 107th (mobile) when clicking “Best” on today's best web novel platform Munpia. It is a work that has never missed the top spot. Based on this popularity, it was aired as a weekend mini-series on JTBC in 2022, and was selected as a research case for this study as a monumental work that achieved the highest box office success due to the success of modern fantasy web novels. The purpose of this study is to analyze the narrative structure that readers are enthusiastic about and how the main character is built and consumed in web novels where commerciality is paramount. Through this study, we would like to present and analyze typical narrative structures and main characteristics that are mainly shown in modern fantasy web novels. Through this analysis, it is expected that it will be possible to derive an understanding of how to increase the readers' immersion and to empathize with and coexist with the main character to further increase the attractiveness of modern fantasy web novel works.