you do the climb like the reverse of a bounce dive in scuba - up and down through the danger zone quickly. the mountain hut is a good way to go but don't expect much - think bunk beds with 5 people per level and a thin pad over a sheet of plywood. And 5 person per Japanese standards. I was with 5 westerners - 4 guys over 6 feet and one guts 5'8 wife. It was tight and my feet stuck off the edge. You may not like it if you are claustrophobic, but in is indoor space to stay warm and nap for a few hours as you start the climb to the summit around 2:00 am. From the huts you can watch all the climbers at night snaking up the trail. Whether you stay in a hut the entire trip is 23 hours or less, but having the hut was a nice break.

How long are you going to be in Japan? I spent 2 weeks/month in Japan for 4 years. I do a lot of hiking during the summers but live in a low elevation area as well. To prep, the weekend before I did two 4,000 -6,000 foot climbs and alot of walking. it's not a technical and is pretty easy overall.