Photography Self-Assignments are a very good idea and are very inspirational for yourself and to others. A few things I would consider that might help are as follows:

Note that these are just things I’ve experienced from my neck of the woods here in Japan. Things may differ from where you are or what you experience.

1. When approaching the administration, I would probably present myself as a professional, but donating free time to work on a self project or something. Japanese people like professionals and I don’t think it would be that difficult for anyone to raise the bar a bit.

2. I would probably have some nice meishi or photography namecards to hand out to everyone involved so they know who you are and where they can contact you of course. It also goes nicely with the “I’m semi-pro or pro but doing some self projects.”

3. I would also have a portfolio to present. Now this can be very basic with some of your “relevant” work to show not necessarily “what” you can do, but what you “like” or aspire to do. I think the administration and anyone with any concern will probably feel more relaxed with a namecard and some photos in hand. You could also use postcards instead of an album. With the summer months coming up, you could create one of those “Summertime” cards for them to hand out.

Finally, if your Japanese is not functional enough, you might consider bringing a friend/assistant who could help with the communication and professionalism. I think everything can be very casual and fun of course, but peppering the experience with prefessionalism here and there just may help to work in your advantage should you have any problems.

These are just some initial thoughts after reading your initial post.

Good idea and please keep us updated on how things go.

Regards,
Jim Atwood