Both tell the story of a theater drama artist's struggle from zero with all the obstacles. But in Jeongnyeon there is a queer element in the story
Rika is a high school senior with no self esteem. She thinks she is an iguana. Why? Her mother claims that whenever she sees Rika she sees an iguana instead of a real human. Because of this, Rika has never received or was shown any love by her mother. Rika's younger sister, Mami, has been getting all of the love and attention by the mother. Rika likes Noboru a lot but can't tell him her feelings. Kaori is jealous of Rika and refuses to let Noboru go out with her. Nobuko is Rika's friend and is always encouraging her. Will Rika end up with Noboru? Will he turn her away if he finds out she is an iguana?
In some views you can't even compare 'Heartstrings' to 'Glass Mask' (there are two seasons), because 'Glass Mask' is better in many ways, but both are about acting and working hard in order to achieve your dreams. GM is not so much about romance as H is, but it shows the reality of being an actor.