When you have enough time to do so, it would be better for you to contact your second-choice lab. However, what we ask you is to contact your first-choice lab in advance to your application.

It's okay to tell them. It is not uncommon for students to be assigned to the laboratory of their second or later choice, and there is nothing rude about it. If you still feel uneasy, you can choose not to tell it to them.

Please discuss anything about your research plan before the end of the application period.
Applicants are not allowed to contact your prospective supervisor between the end of the application period and the release of the accepted applicants by our department.
If you are a research student, you have a right to attend the lab seminar or similar events as a research student, not as an applicant. However, your prospective supervisor may get fired if you step a bit out of research student. So, generally contacting the prospective supervisor between the end of application period and the public release of the list of the Third-Stage Successful Candidates should be avoided where possible.

Yes. Once the department of Computational Biology and Medical Sciences publicly release the list of the Third-Stage Successful Candidates, you are free to do anything.

If you are already enrolled in the University of Tokyo as an undergraduate student, you will be able to attend lectures, do your thesis research, etc. with a faculty member of the laboratory you wish to join. Contact may be unavoidable in such cases even after the end of application period. Undergraduate students have the right to attend lectures and to get guidance on their thesis research. In such cases, we do not prohibit contact as an undergraduate student. However, to ensure fairness between applicants, such undergrad students can contact supervisors only as a graduate student, in lectures, exams, thesis research, and other activities. Avoid one-on-one communication and only in the presence of a third party. Avoid having long conversations. If you need a lot of detailed assistance in thesis research, please ask someone in the lab who is not involved in the entrance exams, such as assistant professors or doctoral course students. The same principle applies to research students and people with other similar statuses.
Please be reminded that you cannot ask someone else (including students) in the lab you wish to join to take a look at your Inquiry Sheet for getting help/advice.

Please directly contact the laboratory you wish to visit in person.

Yes. Visitors are always welcome.