Japanese “light novels” are a type of short and often serialized young adult novel that are usually heavy on dialogue and light on narrative depth. The growing popularity of light novels has made them common choices for manga and anime adaptations, such as the Haruhi Suzumiya series.
Got that?
One of the more popular light novel series in recent years is My Little Sister Can’t Be This Cute, which tells the story of a normal high school student who finds out his prodigious younger sister is actually a closet otaku, obsessed with anime and incest-themed adult computer games…

That would be quite the discovery.
It’s probably less unwholesome than it sounds (at least by Japanese standards), and the point is that the series has become so popular that it has spawned an anime and manga series as well as several video games

It has also seemed to usher in a new craze of light novels about the relationship between normal older brothers and their not-so-normal little sisters.
There's a big audience for this.

at japandailypress.com is not happy about this, but doesn't explain what the actual problem is. People who express disapproval would no doubt be shocked to know how many successful people, including leaders and innovators and artists, are in, or have been in, consanguinamorous relationships with siblings. There no reason why consanguinamorous siblings shouldn't be depicted in media.

Here are some entries from last year about consanguinamory in Japan and depictions thereof in Japanese media.