They have an instant connection and ring each others' alarms.
Duk Gu comes up with the idea of the app in order to express his feeling to Gool-mi.
In the introduction, Brian Chon tells the world that he has added a new feature in the app which will allow people to predict whether a particular person will fall in love with them or not.
Even your deepest emotions are now out for display.
Even before the love alarm and other stuff, there was an instant connection between them and, not to forget, the undeniable chemistry.
But on the same note, he was also insensitive to Jo-Jo's lifestyle and only wanted to have fun.
Description: The app is so popular that it is even incorporated into marriage ceremonies.