Two girls, Cai Xiao Ai, who is battling a terminal illness, and Gu Eun Zhao, a cold and distant girl, come together despite their fates. As they struggle with life's challenges, friendship, family, love, and their future, a hidden conspiracy begins to unravel around them. (Source: WeTV) Adapted from the webtoon "Knife in Her Heart" (칼가는 소녀) by O Ri (오리).