I was watching an anime and one of the characters said this:
I was a bit surprised because I was told that you should connect adjectives with て.
Why is this characters using し here?
When the character said
It roughly translates to
He is nice, plus mature, plus cute.
If you were to use て、 you would not say 優しいて、 you would say 優しくて.
Here, 優しいし is used because it is a little more informal than 優しくて.
I hope this helps.