A corner of my black leather seat has color fading problem and looks whitish in apperance maybe due to long exposure to sun's uv rays. Is there any way to fix it?

 

The black dye on your seat is faded so just re dye it using Kiwi brand liquid shoe polish. There are articles on the internet explaining how it's done with good success. Just make sure you wipe the polish off with a rag immediately after applying. You can try a small out of the way area first to see if you like the process.