(PV) Checkicco - HajimariCheckicco (チェキッ娘) was an idol group that debuted in 1998, the same year Morning Musume originally debuted. However, they didn't meet the same success as Morning Musume, though they had several subgroups such as chee's and METAMO, and were promoted through the TV show DAIBAtteki!. They broke up in November of 1999.
Probably the most well-known former Checkicco member is Shimokawa Mikuni. Yes, Shimokawa Mikuni was in this group, with the number of 002 (each member had their own number). And she began her solo career while she was in Checkicco, too.
Here's the rare PV for one of their singles, "Hajimari", a bittersweet song about graduation.