Complex sentence: After graduating Sookmyung High school at the age of fifteen, she went against her father's wishes to study under modern dancer Ishii Baku in Japan, where she distinguished herself as one of the most talented dancers.
Split into simpler sentences: After graduating Sookmyung High school at the age of fifteen, she went to Japan to study under a modern dancer Ishii Baku against her father's opposition. She distinguished herself as one of the most talented dancers.