AKB48 (from Akihabara district in Tokyo and its original 48 members) is really more than "just" a japanese pop group, they are more like a phenomena. One thing you cannot mention in regards to them is their number of members, which reaches close to a hundred (roughly 90 atm). This means the typical subgrouping here is a must, and still leaves them with more than 20 girls per subunit. It quite fascinating and it of course gives rise to interpolations in regards to prejudices about the collective thinking of societies. I wouldn't go that far, but instead compare them to for example
Irish Riverdance shows. Its just a different combination of music and performance. They have released lots and lots of singles, albums, tv series, and much else, here are a few examples (there are some very popular videos of a more "risque" nature, but you will have to find them for yourselves):