When you turn on the application, your heart will ring.
Love Alarm is an app that tells you if someone within a 10-meter radius has a crush on you. It quickly becomes a social phenomenon. While everyone talks about it and uses it to test their love and popularity, Jojo is one of the few people who have yet to download the app. However, she soon faces a love triangle situation between Sun-oh whom she starts to have feelings for, and Hye-young, who has had a huge crush on her.
Curious about her true feelings for Hye-yeong, Jojo returns to her alma mater in search of information on Chon Duk-gu — and runs into her past.
Jojo asks Brian Chon about the shield at an event attended by the Badge Club members, including Sun-oh. Hye-yeong comes face-to-face with his father.
Jojo offers Hye-yeong a shoulder to cry on after a punishing day. Unable to cope with knowledge of the shield, Sun-oh turns to Jojo for the truth.
With video of his lecture hall visit gone viral, Sun-oh comes to blows with Hye-yeong. Jojo receives a special gift from an unknown sender.
Park Gul-mi reaches a digital milestone. Brian grills Jojo about the shield, spear and Duk-gu — and shatters reality for a bystanding listener.
Revealing the identity and inspiration behind The Ringing World, Jojo reconciles with the past. Duk-gu keeps his end of the bargain.
