BKA48
BKA48 is a special AKB48 unit created from the Mecha mecha iketeru! AKB48 Kimatsu Test. The members are know as BKA48 (BAKA48 - Idiot in Japanese), and were selected from the show as the 7 members who scored the lowest on their tests. They're also know as the BAKA 7.
They're also a single unit, and sing TBA on Sayonara Crawl. Kawaei Rina is the center, as she scored the lowest on her test.
Kawaei also performs in a harness with HASUTE & WASUTE (ハステとワステ).