the plot needs and the director's intention.

1. The story needs: Japanese drama crews think that it is better to focus on the emotional expression of the plot and characters without background music, or that it is better to create a specific atmosphere or mood without background music, which leads to the lack of background music in the original sound of sailing.

2. Director's intention: Japanese dramas can better express their artistic style or express their intentions without using background music, or they hope to leave a deeper impression on the audience in this way, resulting in the original sound of sailing without background music.