Koreyori Tachiiri Kinshi

Rich girl gets engaged to her bodyguard, but does he love her, or is he just her bodyguard?

From Colorful Scans:
Kokona, daughter from the Eda family, and Hiro, the son of Kawai family, who has been serving as bodyguard her family for many generations, were engaged by their parents. She likes him. He seems to feel no feelings towards her. But...