@jackslate I feel like the word "believing" is stronger though while "knowing" seem casual. Believing also include knowing in it because if you don't know the person, how can you believe in them? You have to know them and understand them in order to believe in them.
The Japanese word Shinjiru can mean believe, trust, or have faith in , it is a strong word than the word "knowing".
In anime, manga, movies, literature, tv drama, etc. I see the word "believe" being used more often than "knowing".