Often translated to English as "8th-Grader Syndrome". A similar insult in English is calling someone "edgy".
Japanese stereotypical depiction of delusional people who attempted to stand out by believing that one has special powers (especially sealed powers), a dark past, or such like. Chuunibyou can manifest as overly dramatic hand gestures, expressions, and spoken lines; and clothing such as eyepatches and scarves. If the symptoms are severe enough, even actually having special powers and/or a dark past may not be enough to beat chuunibyou allegations.
Only tag images where a character is actively displaying chuunibyou behavior; do not use simply because the character is a chuunibyou in the series. The tag is not meant as an abbreviation of the light novel series Chuunibyou Demo Koi ga Shitai!.
