Lasmyr
Google
It was a great place to start/end my Yakushima trip. Most of the things you would need would be here (bus pass, trailhead bus pass, information about bento, etc.) and the staff are very nice and can speak English. I think the small exhibit + video is worth the small fee, it is very educational; it is all in Japanese though, so make sure you have your translation app ready. They also have a very nice hiking map you can buy as a souvenir!