Climbing Mt Fuji

From the Fujinomiya 5th station or the trailhead (2400m) to the summit (3776m) takes roughly 5 hours and about 3-4 hours for the descent making it the shortest of the 4 trails.

But don't let that fool you, it's still a challenging climb! Although you'll have less distance to cover compared to the other trials, the ascent is steep and rocky. Though there will be no scrambling (climbing with your hands), the trail features lots of big steps and precarious foot placement.

Additionally Mt Fuji is infamous for its volatile weather. A climb to the summit of Mt Fuji guarantees that at one point you will be dry, wet, hot and cold. From scorching hot and humid summer conditions to snowy winter conditions, one should always expect for the weather to drastically change in an instant. Almost any type of weather you can imagine can be experienced at any given moment on Mt Fuji and being prepared with the necessary equipment will be key for a successful climb. 

Not only weather! Though Mt Fuji is not at an elevation where supplementary oxygen is needed, all climbers will feel the altitude to varying degrees. Some may only experience a slight shortness of breath but other may experience dizziness, nausea or other effects of the elevation which may affect your climb.
*Serious altitude related complications are rare outlier cases on Mt Fuji.  

Lastly, the amount of equipment needed (especially over 2 days) on Mt Fuji tends to weigh down a large backpack (a loaded backpack weighs between 5-15kgs)!

Training goes a long way! It is strongly advised for you to be practicing an active lifestyle spending a lot of time on your feet. Pacing is an important part of hiking big distances and regularly training your stamina and cardio with activities such as hiking, walking, running, stairmasters and cycling will help you towards successfully reaching the summit.

Additionally it is advised to also go hiking/ walking with a 10-15kg backpack to simulate what you would be carrying at all times on your Mt Fuji hike.

In summation, what makes climbing Mt Fuji so difficult is its steepness, rugged/ rocky terrain, elevation, volatile weather and sheer length of climb while carrying equipment.