Might be some issues with her health. We have seen her at the infirmary since the beginning of the series, the phrasing and the look of concern from the school nurse heavily imply that.
if it getting dragged unnecessarily long, It might have a decline internationally but I highly doubt that will happen in Japan. Just look at Kaoru Hana or rent a girlfriend, they still sell a lot of copies despite all the bad-writings, dramas and unnecessary fillers. I believe Japanese people...