From Go! Comi:
When her grandmother passes away, high school student Kajitsu Toda suddenly finds two hot stepbrothers and an adorable little stepsister dropped in her lap! Kajitsu and her step-siblings have only one thing in common: they were all abandoned by their parents. Against the odds, they've pulled together to form a family without grown-ups. They don't want charity, they don't want pity... they just want their dignity!
Things are particularly tough for Kajitsu and her step-brother Natsu. As kids, they were as close as any true siblings. Now, reunited for the first time in seven years, they've grown as far apart as two people can be. Can they ever become friends again? And can two high school students living together, even as "siblings" ever escape scandal?