Wild Ones Vol 1

Wild Ones Vol 1 by Kiyo Fujiwara. A Shojo manga rated Teen, published in English by Viz Media in 2007.

After her mother dies, Sachie Wakamura is taken in by the grandfather she never knew, who turns out to be the head of a yakuza family. Sachie is determined to live a normal, sweet life anyway, with the help of Rakuto, the handsome young bodyguard assigned to protect her.