I’ve been scrolling Crunchyroll News and I just had this thought as I do so: The rise of Osomatsu-san’s sales are actually attributed to the female demographic. That’s just based on the headlines, so let’s delve further.
Although they are not giving out any specific numbers, eBook Japan reports that since Mr. Osomatsu began airing in October of 2015, sales for the original Osomatsu-kun manga have increased by over 80 times what was sold in the previous year. eBook Japan attributes the majority of these sales to the spending power of adult women and to the dedication of female anime fans known as fujoshi. 
Here’s another one —this a subtitle of a Crunchyroll TOWER RECORDS ranking post:
“Osomatsu-san” ED song is mainly purchased by women in their teens to thirties 
I think this was due to the formula that they showed in the first (and the eleventh) episode, which depicts the sextuplets as a male idol group in the likes of Uta no Prince-sama. Or was it because of the male voices behind it?
I may be wrong, but I’d like everyone to think about this as well.
Just to be clear, I LOVE the 2015 series and am looking forward to its continuation next year — I wish they go the Gintama route and just stop when they’ve had enough, (only to continue another run, in Gintama’s case).
I just saw an Anime News Network report on Comic Market 89’s statistics, and it has these words:
Based on Mr. Osomatsu’s popularity on pixiv, [analysis author, Meiji University Yoshihiro Yonezawa Memorial Library staff member, and Niconico Gakkai β executive committee member] myrmecoleon expects several hundred circles dedicated to the series to show up at next year’s summer Comiket. The amount of fan art for the series posted on pixiv during the analysis period was so high that the bar could not be represented on the graph with the other series. 
The said quote refers to this:
Let me take a look at pixiv right now. It doesn’t disappoint, as I am expected to see 400 or so images.
 “’Mr. Osomatsu’ Anime Causes Digital Sales Surge for ‘Osomatsu-kun’,” Crunchyroll News, December 28, 2015 (emphasis mine)
 “TOWER RECORDS Shinjuku Weekly Anime Song TOP 10 December 14–20,” Crunchyroll News, December 26, 2015
 “Dōjin Circle Numbers Reveal Top Series at Comiket 89,” Anime News Network, December 29, 2015