When there are an uneven number of active players for any basho, the Bench Sumo 'drone', 'Kofujinokami'* will enter the competition, in order that every player has an opponent each day.
Kofujinokami will have his squad generated for every basho that it is needed. His picks will be based upon the picks of the other Bench rikishi within his current division, at the time of Friday 2 pm (Japan time) deadline. i.e. Kofujinokami's Yokozuna will be the most chosen by the other bench rikishi within its division (if two or more Yokozuna get equal picks, the higher ranked Yokozuna will be selected for the squad), and will occupy the 4 pt position for Kofujinokami throughout the basho. The two 3 pters will likewise be the most popular picks for Ozeki and Sekiwake, the first 2 pt pick being the most popular Komusubi - in each case if two or more Sanyaku rikishi get an equal number of picks, the higher ranked will make the squad. The remaining 2 pt pick, and the whole bench (from first on the bench to last), will be done in order of the 6 most popular Makunouchi picks. The most popular pick will take the second 2 pt position on the team, and the second most popular the first place on the bench, and so on. (again, if two rikishi have an equal number of picks, the higher ranked gets preference in the line-up). No changes will be made to Kofujinokamis's daily line-up, even if two of his rikishi in his 'points' are facing each other on the actual dohyo.
If one of the Kofujinokami's rikishi goes kyujo, that rikishi gets placed last on the bench, and all the other rikishi move up one spot.
Kofujinokami is eligible for all prizes, yusho etc, and will be promoted / demoted on the basis of his record, as like any other bench player. However, there is a special rule for Kofujinokami, that does not apply to other players. The official drone is allowed to have an infinite number of Koshos in-a-row, without ever getting penalised. I.e. Kofujinokami's koshos will always be treated as though they apply to just one missed basho, which will usually mean (there are exceptions, such as if he ever makes the sanyaku ranks!) that he will keep his current rank going into the subsequent basho.
Kofujinokami can never fall off the banzuke.
The original Bench Sumo drone was named 'Derufidurono', or 'Delphi Drone'. This was because the drone's squad is picked using a 'Delphinic Poll'. Derufidurono was officially retired after the basho of January 2012, with Kofujinokami starting his Bench Sumo career in March 2012.
*'Kofujinokami' loosely means, 'The Spirit of Kofuji'. Kofuji was the shikona of Bob Reimer when playing Bench Sumo. Bob was the original automator for Bench Sumo, and the game intends to forever remember his contribution. Bob died of cancer in 2012. His wife, Barb, has given her blessing for 'Kofuji' to be the important drone for Bench Sumo, so that Bob can continue to play his beloved game.