Hadashi de Bara wo Fume

From Viz:

Poor Sumi Kitamura… Her irresponsible older brother Eisuke keeps bringing home orphans for her to take care of even though they can barely afford their own basic needs! Just when Sumi's financial problems become dire, wealthy Soichiro Ashida enters her life with a bizarre proposition: he'll provide her with the money she so desperately needs if she agrees to marry him. But can Sumi fool high society into thinking she's a proper lady? Moreover, is it worth giving up everything for this sham of a marriage?