I started to read Yaya because it has studentxteacher relationship, but it was a bitter disappointemnt.
At first the plot was catching but soon it became too rushed. And when I reached the end I just thought: "Wait, that's it?". It doesn't have an ending at all and it leaves everything open.
To me Yaya was just a waste of time. If you want to read something that's well sketched and the story line is good, I recommend you to read something else than Yaya.