Kenka Banchou Otome: Girl Beats Boys

What is Kenka Banchou Otome: Girl Beats Boys about (plot, summary)
Hinako has grown up not knowing her parents and thinking she has no relatives. One day, a boy named Hikaru appears before her, and says he's her older twin brother. Hikaru asks Hinako to take his place at attending a famous private all-boys academy for delinquents.