Mature? The character design is generic high-lighted colouring and it's pretty less detailed, not to mention how some faces are deformed. And instead of drawing the backgrounds, it's blurred photoshop. If it got this far is because it's a genuine series and the genre Iyashikei (Slice of Life) is a big thing in Japan, if you read the manga you'd realise its potential. The only reason the previous studio stopped animating was bankruptcy due bad managing/practices, like most studios (in fact, the workers were those who put a stop after not being properly paid or paid at all). They are aging of course, but to the point of thinking they graduated in a year...
The only thing that hasn't changed is the voice actresses, which are great all of them. The OST is an imitation basically.
