Mana
I'm sorry to tell but this bus is only during summer season (Jul. 01- Aug. 31) operated. Please read some articles. Climbing Mt. Fuji during the winter is not really recommended for the beginners. If you look up some tours, there may be some optional tour that takes you to the mountain. Hope you will have exciting days in Jpn. :)

bluemoonmemory
There's no public bus service to 5th station(Kawaguchiko) at Mt. Fuji in FEB. The driveway is often closed without pre-notice till early April for Snowing and icing. If you drive by yourself or get a cab, you may get there if you are lucky. Mountain trails are only available for experienced full equipped climbers. It is not like Mt. Takao as you can go on the top easily in few hours.