Son Chaeyoung is a boy, diagnosed with selective mutism. He is bullied at school. He lives with his single mother, Park Jihyo, who has to take multiple jobs a day to sustain their living.  Myoui Mina is a rich girl from Japan. She recently moved to Korea because of her family's business. That's where he met Son Chaeyoung, the silent boy. What will happen when these two cross paths? Will they develop a friendship? Or will they remain as strangers?