How should I approach a Tokyo University professor to join their lab? What are the guidelines that I should follow when contacting a foreign University professor to ask for joining their lab?
I need to find a professor for my already accepted semester abroad as an exchange student. I will be doing my Final Year Project as an undergraduate student and I am having a hard time getting a response from the professors at the Tokyo University. I have contacted with the current student abroad and he told me that it also took him a while to find a professor.
So now I'm wondering about my methods. Is this letter okay?

Hello _____,
I'm an exchange student from the Polytechnic University of Valencia. I am contacting you to see if you might be interested in accepting me for doing my Final Year Project.
The project I would like to do is an artificial skin capable of registering different pressure points on a soft material layer. It would consist mainly on a foam that has resistivity variable with the pressure and an Arduino circuit to read and process these values. In this way we can read many points of pressure in a precise way.
The main challenge is joining several fields of Engineering, which is also one of the strongest motivations for me. I have broad experience in programming, I am confident of my capabilities in electronics and I have already verified that this material is the right one.
There are mainly two fields where this technology could be very useful:

Medicine: For the people who are missing a limb, this could bring back a part of the sensibility, even if it's in a different format.

Robotics: relying on precise pressure sensors could improve greatly the accuracy of many of their functions.


Would you accept me as a student to develop this project? Seeing your background I think that you might be interested.
Thank you so much for your time,
Francisco Presencia Fandos

The main feedback I've already gotten is that if I write the letter open to suggestions but not proposing a project it would be easier for the professors to accept me. Also, I'm thinking of writing my achievements so far, but I think they could look like bragging.
Is this letter okay? Is this the right method for finding a professor in an university abroad?
For professors in Japan, taking on students is a tremendous responsibility and burden. Unlike in the United States or Europe, professors are responsible for even the extracurricular activities of students (i.e., getting arrested; showing up drunk and groping someone; having an apartment so messy that the landlord complains, etc.). They are also responsible for the student's career after they graduate. 

So faculty are noticeably reticent to take anyone on that they do not know or that do not have anyone to vouch for them. It's in this context that letters of introduction from known faculty are extremely important. 

This is very hard for outsiders to break into. Your best hope is that one of your professors knows somebody at U-Tokyo, or knows somebody who knows somebody at UTokyo. It's their letter of introduction that will open doors for you.

Cold-calling will not yield many good results. 

Without a good letter of introduction, your next best strategy is to enroll in either a study-abroad program / exchange program with U-Tokyo that has open enrollment or to apply to one of their English-speaking graduate programs. Going through their international programs office tends to be much better as the staff are used to international norms for student applications. Unfortunately, most of these programs aren't in engineering, but at least it gets you a  foot in the door.


Edit: From the discussion, it became clear that the OP has already enrolled into an engineering program at U-Tokyo that caters to foreigners. In this case, it's the program's responsibility to find him his advisor, as it is clear from their FAQ: 


  "As an applicant for all courses, it is not necessary for you to
  contact a prospective supervisor in advance. Instead, after evaluating
  your application documents, we will allocate you to a field of
  study/faculty member which will be most appropriate for your research
  and research interests. "