Chunibyo is the term for when a person has delusions of having powers, hidden knowledge, etc. The term roughly translates to "Second-year syndrome" since the most vulnerable are students in the 13-14 ages (the ages of eighth grade), which is around the second year of middle school (most commonly around the end). This term was popularized in the manga/anime series, "Love, Chunibyo, and Other Delusions" (or Chunibyo, Chuunibyou, Chu-2, Chu-2-byo, etc.).

The story follows a former Chunibyo victim by the name of Yuuta, he wanted to start anew after his delusions in eighth grade. So he tries his best to forget about it in his first year of high school. But another student (who still has Chunibyo) named Rikka finds out about it and sometimes spills the beans about it to some people, angering Yuuta.