There are a lot of variables that can cause this.
It could be that you are listening to music with the volume too high. It can cause damage to your hearing. It could also be your headphones. If you are using cheap ear buds, they may have a very tinny, sharp, treble heavy sound and Ayu's voice is really pushing the limits. If you are using EQ settings on a music player I would try setting it to Flat and see if that helps. Also mastering/mixing is awful these days. The dynamic range is killed when they create the final version of the song that is released to us. Music is literally louder today.
When I first heard forgiveness I also had to turn the volume down because it was a bit much for my ears.