a person who appears to be totally carefree, etc etc, but is actually really sweet and caring and all the things a girl wishes for.

To be delicious. Asians say "derishious", so this has been shortened to just "rishus".

Rishu is used to describe a useless personality. Someone who appears to be useless as well as a loser. Rishu can is used as a derogatory term and is highly insulting.