Hajime-chan ga Ichiban!

Hajime Okano is an ordinary—or maybe below ordinary—girl who has been forced to take care of everything in her family since she was young because the Okanos are very poor. Hajime has five younger brothers who are quintuplets, and they are scouted by a music company. Thus, this realistic yet dreamy older sister has to try harder to watch over her restless brothers and to pursue her own idol, who works for the same company. (Source MU, edited)