You may want to consider getting a flash light, or a head lamp for your hike up Fuji. It certainly can get dark on the mountain at night.
Personally, i didn't use mine all that much, cause there was a full moon and there were so many people around me using them that everything was very bright, but it was good piece of mind to know i had one.
There's been some reports that tour guides have bullied climbers not in their group. For example, my girlfriend was told by a tour guide that she couldn't sit on a rock and rest because that was a place for his tour group. Total BS.
I've also heard stories of tour guides trying to prevent other people from going ahead of the tour group, which makes no sense to me.
If a tour guide says something like this to you, just ignore them. They aren't the kings of Fuji nor do they have any authority or right to tell you what you can or can't do.
If you start too late or walk too slow you might find yourself stuck in a line. Believe it or not, Fuji has traffic jams, especially near the top where the path is narrow and everyone wants to stay for the sunrise.
It is entirely in the scope of possibility that you will get stuck in line waiting to reach the top and miss the sunrise.
How to avoid this....
try not to get stuck behind those really slow tour groups. Pass them when you get the chance.
Start early, about 6 or 7pm. that will give you lots of time to walk slow and make it to the top.
Try not to stop for too long.
Or, start in the day and sleep in one of the cabins at the 9th station... wake up at 3am and you will make it to the top fine.
The human body requires some time to adjust to a sudden increase of altitude, otherwise there is a risk of headache, dizziness and nausea. Quite a few people, who climb Mount Fuji, fall victim to altitude sickness, like me.
To avoid altitude sickness, climb Fuji at a slow pace and make frequent breaks. Its not a race, though it can feel that way at times.
Bring small bottles of oxygen, available at the 5th stations and mountain huts, can be an effective tool in preventing and fighting altitude sickness.
A sad truth... Mt. Fuji is huge garbage dump. Its true and its a huge embarrassment to Japan. There are weak efforts to correct this problem, but it is what is. My point is, you don't have to add to the problem.
There are NO garbage cans on Fuji.
You should be aware that what ever we take up the mountain you should take down.
No littering of leaving trash on the mountain.
There are four 5th stations on different sides of the mountain, from where most people start their ascent to the summit: Not so much a problem for the start of your hike, but rather a problem for the end of your hike.
From the top of Fuji there are only 2 trails starting down to the 4 different stations. Half way down the trails will split, but it never fails that someone will go down the trail and end up a few hours away from where they should be.
I went with a group of 15 people, and despite my 4 warnings during the trip, one of my party members went the wrong way at the split and ended up in a different prefecture. D'oh!
BETTER PAY CLOSE ATTENTION TO WHERE YOU NEED TO RETURN TO!
There is no toilet paper in the bathrooms on Fuji-san, so you better bring your own.
Also, the bathrooms are all pay per use, so better bring some 100 yen coins with you.