Mekakushi Dan: Watchers (メカクシ団:ウォッチャーズ Mekakushi-dan: Uotchāzu) is an ARG (Alternate Reality Game) campaign that lasted for a month and a half in Summer 2014. It ended in a Nico Nico Douga stream on September 28, 2014.
The series features a few new characters. The first is T-san, an author with poor book sales and a friend to the Mekakushi Dan. The Mekakushi Dan make him help them find a missing girl named Sasha, so they put him in charge of the event and their website. The third character is "watchers", which was made up of those who participated in the ARG.