A seemingly ordinary working mother secretly lives as a legendary sniper who delivers justice where the law fails. After returning from a three-year hiatus, she must balance protecting her family with eliminating dangerous criminals, all while a determined journalist and a relentless detective close in on her hidden identity.

Right after Ryu Sun-jae, a top star, ends his life, Im Sol, his top fan, somehow ends up at a time when they were in high school and tries to protect him. A fantasy romance unfolds where people who missed each other in time finally meet.