Being no stranger to starting from 2nd season, I looked into the Chuunibyou pera pera REN. There was a number of misconceptions thrown about it, such as the arrival of another girl being the catalist for the season (SPOILER: not so).

The main hook really is the management of an insane girlfriend, somewhat like ef: Memo [1]. This is opposite from Nazo no Kanojo X, where the dude is along for the ride and just struggles to survive. And while Chihiro of ef was clinically disabled and had to struggle to function, with the help of her man, our female lead, Rikka, is merely disturbed and only needs a general supervision and safety net [2]. Still, an interesting angle in Chuunibyou is the spectrum of chuunibyou sufferers: from those who control their conditions all by themselves (such as Morisummer), through those who would be well cured by good paddling (see Jerome K. Jerome on depression), all the way to Rikka. There's quite a bit of The Beautiful Mind thing going on, althogh not as serious, certainly. It is a typical anime, after all.

One can also watch REN for comedic hijinks, which appears to be Tappan's approach.

[1] Other examples of the main idea exist, such as the Yukiho branch of iDOLM@STER.

[2] Also, Chihiro's eyepatch covered a ghastly wound scar.