三人祭 (Sannin Matsuri) was one of three special "shuffle units" from Hello! Project in the summer of 2001. They sold the most singles out of the three groups. The shuffle theme was "summer festivals" and they had a cute beach-themed song. They released only one single, "Chu! Natsu Party" (チュッ！夏パ～ティ; "Smooch! Summer Party") which included their version of a c/w song that was shared by all three shuffles. True to their name, they had three members. Read more on Last.fm