The Dolphin in the Little Mermaid

When I was a little girl... I thought I was the main character of my life and the world revolves around me. But?!
Eun So is the most popular boy in class. His best friend is Eun Young, an introverted girl. However, since a short while his best friend is avoiding him. He does not know what to do to reconcile with his friend.
(Source: 초콜릿박스미디어 in YouTube; real_Mokona at MDL)