"Harem Lodge" by Shizuki Fujisawa 2 volumes
As per her father's will, Midori has to live under the care of Tetsuya until she turns 20. She founds out he lives in a boy's lodge and he is actually her fiancee! Cute art and funny start from the first two chapters. But i'm not sure if it qualifies as reverse harem since some of the guys are far from bishies eewww!