This study examines the characteristics of the Japanese web novel genre "Isekai" through data-driven analysis and explores its cultural and social implications in contemporary Japanese society. Isekai is characterized by narratives where characters transition from the real world to another world, beginning a new life. It serves as a means of vicariously resolving unfulfilled desires and conflicts from reality, reflecting the desires of male readers. By analyzing Isekai web novel data, this study identifies that Isekai predominantly features high fantasy settings, narratives of adventure and settlement, and the use of "cheat" abilities as core elements. The analysis confirms that the genre caters to the fantasies of male readers. The case study of Mushoku Tensei reveals explicit depictions of male-centric sexual fantasies, portraying male-convenient sexual ethics, such as polygamy, in a natural and positive light. These sexual fantasies can be interpreted as a compensatory psychological response to suppressed masculinity in modern Japanese society, influenced by a stagnant economy, natural disasters, and the rise of women's rights. In conclusion, this study empirically demonstrates that Isekai reflects the desires and cultural trends of contemporary Japanese society, fulfilling male-centric fantasies. Isekai plays a significant social and cultural role in modern Japanese popular culture. Keywords Isekai; Web-novels; Data Analysis; Sexual Ethics; Mushoku Tensei; Shosetsukaninaro