Togashi Yuuta suffered from chuunibyou while he was in middle school. When he graduated, he put that dark history behind him and forgot about it... or he was supposed to. High school was smooth sailing and full of enjoyment — until the unavoidable, sad event occurred. The event that locked Yuuta into a contract with Takanashi Rikka and disrupted his desperately ordinary life.
(Source: Adapted from the back of the first novel.)
Note: Chuunibyou means "Middle School 2nd Year Syndrome". People with chuunibyou either act like a know-it-all adult and look down on real ones, or believe they have special powers unlike others.