Thread:ShockwaveDude120/@comment-29644557-20180513193605/@comment-24097388-20180513194829

Seinen cannot be viewed by anyone, nor is it marketed for does below the ages of 17-18. Seinen is meant for young adults, going from ages 18-40 (according the TV Tropes at least). This is the age group where you can find hentai and graphic content. This is where series such as Berserk and Tokyo Ghoul fall into, which feature graphic content. One Punch Man is no exception to this.

Also, what source are you using that One Punch Man is rated PG? Because MyAnimeList has it rated as R as shown here: https://myanimelist.net/anime/30276/One_Punch_Man