I headed down to Jangle Jungle over the weekend and whilst the conditions weren't ideal it seemed like a pretty fun, youth orientated mountain. The music was pretty good the whole time and there was a DJ booth in the main building so I assume sometimes they have people play live sets. It was just pop music while I was there though.
It's a small resort with only 2 quads and 1 pair lift but from these there was a fair bit of variety in the terrain and courses. I rode through the park once and there was 3 decent sized (5-7m) kickers, a couple of smaller ones, some mini hips and a few rails/boxes. There were plenty of good riders in the park and it was fairly crowded which I guess comes with being so close to Sendai.
I spent most of the day on the far left (looking up) of the mountain as it was less crowded. There was a couple of small beginner kickers as well and it seemed as though there were plenty of easily accesible tree runs. The snow was really wet and heavy so I didn't try the trees, however there seemed to be good base coverage and no dirt or grass poking out.
Down the far edge a snowboard cross course was set up for a tournament (the reason I was there). Not sure if that is permanent or not but it was a fairly easy course with only waves and some banked turns which was open to the public. They will be constructing another snowboard cross course there in the coming weeks ready for the Tohoku Taikai (Northern Japan Tournament) but I imagine it will be off limits to the public.
Overall it seemed like a pretty fun mountain and is really easy to access by car from Yamagata or Sendai. I was unlucky with weather but will be heading back soon so may update.