Actually I've known them since 2009. I accidentally found Ai Ai Gasa PV on youtube and I loved it because the PV and the melody are so sweet. But I didn't really follow them. And then about a month ago, I tried to listen to their first album album "Tegomasu no Uta". I liked it so much that I decided to download all of their album. Then I asked my friend to give me the copy of their concert. My impression after watching their concert was they are such a great singer. They sang all of the song live. No recording. Then I decided to download their 2nd and 3rd concert. It turned out that their concerts were really good. Especially the 3rd one. The stage, the lighting effect, their outfit were soooo good. I love it so much. And now I'm watching it again and again.
[some performances on the 3rd concert:]
[bonus pics of them:]