Board Thread:Questions and Answers/@comment-76.88.34.229-20140708185559/@comment-98.221.208.172-20140709020317

I don't really know if this helps but just to add on to what Starikun said:

Circle Of Friends ( aka COF ) started out when Amatsuki ( who is the leader of the group ) said in a Nama with Hashiyan that he wanted to go on a bus tour with all of his friends and people seemed to be really supportive of his idea and then stuff happened and his wish came true. To join the group, I would assume that anyone who is a friend of Amatsuki or is in their friend group is welcome to just tag along and sing with them on the tour. Since most of the members are friends with song producers or produce songs themselves they do have some original songs on their albums and such in which they sing.

If I recall correctly Smiley is the name of the company/record company that I assume is in charge of all the Smiley groups which is where the Smiley part of the name comes from ( please correct me if I am wrong ). As Starikun said the groups are formed around a concept, Smiley*2 is a group where everyone is a member of a host club and is separate from Smiley 2*G and Smiley 2*GS which are based around a school concept where everyone is a member of St. Smiley Gakuen. In Smiley 2*G everyone is a member of the school's student council and In Smiley 2*GS everyone is in a special performance class that makes up an idol unit called HEAVENS DOOR which is lead by Amatsuki/Amanogawa Kakeru. In each group each person takes up the persona of a different character and they sing songs/character songs for their character and do voice drama's( Think of it like a drama cd for an anime or something ). They will also sometimes dress up as their character and perform concerts  and videos as the characters in their group( this is mostly in Smiley 2*G  though since they are the most active out of the 3 groups).

The only person who has ever "graduated" from one of the groups was Shounen T ( aka Honokaze Tomohisa ) who left Smiley 2*G but I believe left because he was retiring as a utaite due to his record deal and becoming a professional singer.