Meaning of the song

Kaze Fujii explains the meaning of the song in "Kaze talks about "YASASHISA"".

"YASASHISA" means kindness. It's basically a love song for kindness. And when I the moment that I was treated so kind be someone when I wasn't so kind to someone I felt really ashamed of myself. That experience was the inspiration for the song. That I realize that kindness is not weakness and kindness is strength. kindness is damn ass. So why don't we live life of kindness together? Why don't we let just let ourselves just be kind to one another.