18-sai, Niizuma, Furin Shimasu.

Umeka is the heiress of the powerful conglomerate known as the “Sanjo Empire.” She has never been in love, but upon graduating high school, she will surely be forced into a suitably arranged marriage. Before that happens, she decides to fake a marriage with her bodyguard, Kira. It seemed like she was going to get away with the scandalous relationship, but... (Source: Shogakukan, translated) Note: Includes 10 extra chapters.