Yukino is a shy and sickly person who was born with a lung disorder causing her to go into frequent coughing fits. Her parents thought traveling might help her recover... Which is why she became a trainer. She met Bolt along the way and, started traveling with him. She soon had feelings for the overconfident and always active trainer. When Bolt had to leave suddenly for unknown reasons her new goal was to find him. Traveling with a new determination and goal to achieve Yukino got her health back in shape and became a great trainer along the way.