This article examines how people view language use in manga (Japanese comic books and graphic novels) through an analysis of posts on a Japanese online bulletin board system. The analysis uncovers three central assumptions regarding texts understood as manga: they lack linguistic sophistication; their linguistic authenticity is problematic; and they negatively impact real-world speech. In the posts, language in manga is often assigned a vaguely negative influence on communication skills, and engagement with manga is foregrounded as a problematic social issue. Beliefs about language in manga parallel commonly held beliefs about language used by otaku ‘nerds/fans’, suggesting that metapragmatic stereotypes have expanded from media users to the media itself. Such criticism often targets women: although otaku are normatively viewed as male, women seen as encroaching masculine forms of engagement with manga may also receive criticism. The article thus contributes to an understanding of how perceptions of language and gender in media are formed.