Thinking of hiking to Jomon Sugi? If so, you need to know this. The entrance to the A1 Trail which is the main trail used to hike to Jomon Sugi has access restrictions to try and lessen the environmental impact of tourism on Yakushima. Basically you cannot just drive there any more. You either need to take the special Arakawa bus, a pre-arranged taxi or be on a guided tour. You can of course by-pass this completely by taking the K1 Trail past Shiratani Unsuikyo and meet it further along the valley.
The following PDF has all the details: