Yamagakure no Shiro

The Castle Hidden within the Mountains (山隠れの城, Yamagakure no Shiro) is an ancient base which all Nanabake business is conducted. From training to actually living, it is a massive string of hidden castles built into the Land of Wind. Yamagakure no Shiro's secrecy caused thousands to question it's existence. To children of Sunagakure, Yamagakure no Shiro has transformed into a variation of hell. A story told by parents to scare bad children. That those who disrespect their elders will be snatched up by masked Shinobi. And tortured for all eternity. However, the Yamagakure no Shiro is the exact opposite. Despite it's external menacing appearance, those who call it home are actually filled with happiness. They consider one another as family, which is important seeing as most Nanabake agents are Orphans. They are taught to love one another. Protect each other, and even become lovers. The death of a Nanabake sibling is often a tearful occasion.

All branded with the Nanabake's calling symbol are able to teleport directly to base through a string of seals. Also, they can access it spiritually to accept missions and contracts sent through a special scroll based communication system....Those who are not blessed with the Nanabake contract are trapped in a unique genjutsu brought upon by a massive barrier...

Trivia

 * Similar to the Nanabake founder, the Castle Hidden within the Mountains is a reference to the actual Hashashin castle.