Kogane are small light blue colored shikigami with skull-shaped heads, cylinder-shaped bodies, and wings. Each Kogane also has a black tail but they differ from one to another. Kogane can differ in other ways as well, such as the shape of their eyes or added facial hair. They're capable of speaking and each of them even possesses semblances of personality.
Each Culling Game player receives a Kogane that services them as their main point of contact with the Culling Game. It goes over the rules with each player and tells them every time they've scored points. Any non-players who decide to declare participation will need to confirm with Kogane upon entering a barrier colony. Kogane also allows the players to contact the game master in order to negotiate new rules. Kogane will announce newly added rules to their players in a different voice than when acting as a liaison for a player.
As the Culling Game's main interface, Kogane is capable of adapting to each added rule to the Culling Game. For example, when the rule allowing players to access each other's info was added, Kogane gained the ability to change its shape and display player information on command.
Yuji was first introduced to his Kogane when it announced that Hajime Kashimo added a new rule allowing players to view each other's information. Yuji and Megumi used the new rule to have Kogane show players with one hundred or more points. This allows them to prioritize Hajime Kashimo and Hiromi Higuruma as targets so they can use their points to add their own rule to the game with Kogane.
Upon attempting to enter Tokyo Colonies No. 1 and 2 on November 12th at noon, Yuji, Megumi, Kinji Hakari, and Panda were all asked to confirm their participation in the Culling Game. Before entering the Tokyo No.1 Colony Kogane warned Megumi that a lethal contest called the Culling Game has begun inside the barrier and entering would make him a player. With Yuji already considered a player, Kogane only required confirmation from Megumi. He agreed to enter the game and said that going over the rules wouldn't be necessary, appearing to annoy Kogane.
Hiromi agreed with Yuji to use his points to add a rule that allowed the transfer of points between players. Using Kogane, Hiromi negotiated with the game master that this rule would affect rule eight involving Cursed Technique Removal. The rule was approved as the tenth rule of the game and Hiromi used his Kogane to transfer one point to Yuji. At the same time, Megumi and Chizuru Hari's Kogane announced the new rule addition to them. Megumi eliminated Hari shortly afterward and his Kogane announced he scored five points.