Heart rate monitor watch is a personal monitoring device which allows a subject to measure his of her heart rate in real time or record his or her heart rate for later study.
Dokkojin wears a heart rate monitor watch to monitor how fast his heart beats. After having heart surgery, he is always careful to try to his heart rate in the safety zone of 60 – 90 beats per minute.
His heart rate seems to elevate whenever Gu Ae-jung is around or when he hears the 두근두근 (Thump-thump) song. Not knowing what love is, he associates his heart beating as an indication that he likes Gu Ae-jung even though he’d like to deny it.From Dokkojin’s watch getting broken and allowing him to stay within the safety zone (despite his true heart rate) and testing out Gu Ae-jung’s true heartrate, it acts as an indicator for Dokkojin to realize and assess what he is feeling.