Will I be able to store baggage anywhere before climbing Fuji?

Once we have left Tochomae and Gotenba station there will not be any place to store your extra baggage. Options for luggage storage include, coin lockers at Shinjuku or Gotenba station, hotel baggage storage services or sending by 'takkyubin' (postal service) to your next destination. Mailing your bags to your next destination is surprisingly cheap at about US$20 for next day shipping for any check-in sized bag. You can mail your luggage from your hotel counter (most common) or from any Seven Eleven convenience store in Japan! Here is a webpage with more information.