[dragontamer]

Common yes, but not as common as it has been in recent years.

Three title-character Hikikomoris in a single anime season? Especially sine most of the examples before 2009 are not title characters. IE: You get stuff like a specific client for one episode of xxxHolic in older animes... or Haruhi who insulted normal people by calling them Hikikomoris.

But in contrast to say, Spring 2014 animes, there are three title character Hikikomoris that play major roles in the anime.

The concept has always been in anime, but very rarely has it been used so often for main characters.