Ikeuchi Hikaru works for a design company in Tokyo. One day, she gets a proposal from her assistant Okugawa Kota, who is also her boyfriend. He can be a little irresponsible, but he is very nice and loves her wholeheartedly above all else. Hikaru feels happiness. Meanwhile, Hikaru represents her company and takes part in a construction company’s logo design competition. At the orientation venue, Kota gives a very nervous Hikaru a kiss in the elevator for encouragement. However, the lift doors unexpectedly open at that moment. Hikaru’s gaze to slides to the door and she finds herself unable to take her eyes off someone standing outside the lift. He is Moriyama Shin, a designer of a rival company, whose former surname was Oda. He is the man whom Hikaru had once loved to death. But he vanished all of a sudden three years ago after telling her that he liked someone. Although Hikaru should be comforted by Kota’s presence, her memories of Shin come gushing forth. However, she has never had reason to tell Kota about this. And so, she is the only one agitated by her encounter with Shin. Furthermore, that day becomes the turning point and begins to cast a pall on her happy life. The feelings that Hikaru has tried to suppress are rekindled and her heart seeks him even though he is now married with a wife, Ran. As this happens, Kota’s love and jealousy deepens and he gradually turns into someone he hates.