Travelling during Golden Week

Availability of trains is not a problem. Getting a seat on some crowded lines might be. But if you have the Pass, you can make seat reservations ahead of time at no additional charge on bullet trains, as well ltd express and a few others. Plus in smaller cities you will find less crowds, unless they are at the most popular tourist spots and hot spring resorts. You don't say how much farther south you want to travel, but just beyond Miyajima is Iwakuni, with its iconic bridge and mountaintop castle:

https://www.youtube.com/watch?v=0COOZXi66mM

If you want to escape the crowds, then getting off the beaten trail is great too. Few venture to Onomichi, with its temple tour and wildly colorful Kosanji Temple:

https://www.youtube.com/watch?v=97Q5EjEOXI8

And Shikoku is also a rarely visited gem. The Trek up Kotohira is a great day trip:

https://www.youtube.com/watch?v=ley9rVIewoQ

And of course, Kyushu has numerous sites that few venture to go see.

Thanks a lot!!! Honestly much much appreciated!!! I did not know I could reserve ahead of time, I thought I would have to do it all together once I get to Tokyo. The days start counting after you actually take the first train, is that right?

After Miyajima the plan is to head for Kagoshima, then Fukuoka and then back to Kyoto and finally Tokyo. But I will definitely check the places you have mentioned!!!

Again, thanks a lot, hopefully I will get to reserve the trains.

Best regards,

Lisandro

The days start counting after you actually take the first train, is that right?

Not exactly. You must exchange the voucher for the pass at a major JR station or office. When you do that, you must advise what date you want it to begin. Many people of course exchange it right before taking their first train, but for example if you wanted to start using the pass the next day from a smaller station that can't exchange the voucher for the pass, it is also possible.
The days don't actually start counting from when you take the first train - they count from the date you designate when you exchange the voucher into the pass. Then the dates start being counted, whether you take a train or not. A day starts and ends at midnight - so if you activate your pass at 6PM, your first "day" is just 6 hours.

Kagoshima has many good sights to see - especially Sakurajima, as well as the beautiful Senganen Garden.

https://www.youtube.com/playlist?list=PL7LcPcmoSg-irtXXB8IJMdkB9mF0qjnqK

Fukuoka also has a number of good places to see:

http://www.thejapanfaq.com/fukpic.html

https://www.youtube.com/playlist?list=PL7LcPcmoSg-j4RLa6iC7ayvBAbOn8-028

Be sure not to miss the Nanzoin Temple there - it is a secret jewel that few know about, and FREE:

https://www.youtube.com/watch?v=lT4VQFmHFyM

Thanks again!! Yeah I thought of starting to use the pass the day following my arrival at Tokyo (because that day I would only be taking the Narita express and I do not want to waste a full day on just that).

Thanks a lot for the info on these places!!

Best,

Lisandro