When you reach lv.40, the first blade Zangetsu will be unlocked. Altogether 3Zanpakuto can be shown in the battle.
Every Zanpakuto has 3 different forms, stats will rise with every level up. Slot which can store Soul Crystal will also be unlocked. Crystals of the same attribute cannot be placed into the same blade.
The second Bankai Senbonzakura will be unlocked when the first Bankai reaches lv.4. The third Bankai Hyōrinmaru will be unlocked when the first or second Bankai reaches lv.7.