Yunyong has the unique ability to see "jellies," invisible entities that can be dangerous, prompting her to become a school nurse at Mong Leon Gymnasium to help children combat these threats. One day, a boy named O Swang Guan learns that his crush, ARA, might be asked out by a rival on the basketball team, prompting him to take action.

As he rushes to find her, he feels a strange sting in his neck and visits the infirmary, where Yunyong removes a heart-shaped jelly from him. However, before she can explain the treatment, he bolts out of the room. Determined to help, Yunyong follows him and finds him waiting right outside the door, setting the stage for their next encounter.