Earlier this week was the season finale of this series.
According to the picture you are seeing, There should be a litle teaser about a season 2 of this anime and that teaser was on the last chapter of this anime.
As you can see on the right of the picture or on the next picture more closer shot.
It reads “Nikki Kettei” Which is the romanization of the japanese words, which translated become something like “Season 2 Confirmed”.
To add alitle more of that, On the newest manga chapter of this series ,which came out on September 19, there was something relationed to the Anime (Here to see the pic).
Still, the thing is a rumour, and until it is formally announced it will stay that way.