The mountain hut reservation service FMG provides is available starting April 1st for reservations of the same calendar year July - Beginning of September. Available dates for a reservation at the Fujisan Hotel can be viewed on our website here starting April 1st. There is a service charge of ¥1,000JPY per person to secure your reservation at Fujisan Hotel.
Alternatively, a mountain hut reservation can be made on your own by phone, directly through any of the mountain huts on Mt. Fuji. For information on huts on Mt. Fuji, including opening/closing dates as well as phone numbers, check out this page on the JNTO website.