Dante404 I'm happy to help!
Visa arrangements depend on many factors, such as the country which issues your passport, the terms of the internship or job offer, and of course, the length of time of the internship, among other things. Additionally, with the current restrictions on travel into Japan, policies look a little different from normal and are continuously changing.
Because of these reasons we typically handle visas on a case-by-case basis and we are only really able to provide more concrete information if and when we are able to reach the internship/job offer stage. Generally speaking, the differentiation between full- and part-time is not necessarily as important when it comes to visa paperwork, but this will be subject to whatever policies are in effect at the time and whether or not a hiring company is able to facilitate such an arrangement.
With regard to continuing on to a second internship, it is certainly not an issue with our program, per se, but please be aware that it may be very difficult to arrange as we are unable to guarantee that candidates will receive an internship offer. Either way, we are happy to assist with continued internship and job-seeking efforts. There is also the possibility that this may affect visa arrangements, but again, this will depend on factors determined closer to an actual offer.
I'm sorry I am not able to provide a clearer answer to your questions, but please rest assured that we will be available throughout the entire process to assist with all visa and internship arrangement matters.
Please let me know if I can help you with anything else!