The core of AKB48. They were the very first members of the group, known as Akihabara48 at that time. After the 2nd Generation was introduced as (the original) Team K, they were known as (the 1st Generation) Team A.
In the Manga version, Takamina was the one who asked Acchan what she'll do after her graduation.
The 1st Generation members were then invited by Acchan to her new office and were the first to know about Acchan's decision to become a detective.