I want to pursue a PhD (in the area of Biophysics/Condensed Matter Physics) and I have contacted several professors at the institute I want to study (University of Tokyo). From personal experience, I know lab websites don't reveal personalities of professors, in particular, it is not possible to discover whether a professor is pleasant to work with. How can I determine whether a professor is pleasant? In particular, how can I identify the professor most favoured by their students? Also, how can I identify professors to avoid?