The mobile “fan club” site actually pre-dates the official fan club site by a bit. It used to be the main way for staff to distribute photos, downloads, etc. behind a paywall. With the coming of the Ro-Gumi site, the mobile site has languished for several years. It’s still technically active, and there are certain benefits that have been added (special download photos at live events, extra chances for the meet and greet, etc.), but not much has changed.
However, with the 15th year approaching, staff have revamped the site, and changed the pricing a bit to reflect (hopefully) upcoming goodies. The previous fee, 330 yen per month (tax included), will now become the basic membership tier. This tier can listen to the Bararaji radio show and view basic links like the discography, staff blog (still empty) and the biography page.
There’s now a new membership level, premium, which costs 440 yen (tax included). This level provides access to movies (there one so far), the Bararaji request form, special messages from Kiiyan and e-zuka and more.
Membership can be paid for via Docomo, AU, Softbank or credit card (foreign cards probably not accepted, based on the form). If you’re already a member, you have to cancel the 330 yen membership before applying for the 440 yen membership. There’s a function on the site to allow you to retain your membership ID and ranking (e.g., Rodeo Joker).