Two girls are friends, sisters, and soulmates. Yu Qi, a 17 year old high school student, wakes up to find that she and her 27 year old self had switched souls. One has to relive the experience of meeting her lover again and the other has to bear the responsibility of being her girlfriend, despite the unfamiliarity. Both worlds are always changing, but the only one who never changes is... you, who is always by my side.