Lin is a Shut, destined to a life of undying love towards one person. Dosung is a Destroy, always on edge to hide the violent outbursts they're known for. In this world, it's not just the genetic, but also the psychological traits that distinguish them. Just as Lin is coldly rejected by Dosung, a string of horrific murders threatens their lives and the investigation creeps ever closer. Everyone has a secret in this society of differences, but can Lin turn Dosung around? The countdown begins in this gripping romance thriller.

340 Days began as a webtoon submitted to Naver Challenge and then serialized on Lezhin Comics Webtoon, and was officially published in book format by Wisdom House (위즈덤하우스) on May 30, 2018. The series was published digitally in English by Tappyton.