Tanjiro is very kind by nature and has been described by others as having very gentle eyes and a compassionate persona. He exhibits a great deal of determination and will not give up once he has a goal to achieve; the best example of this being his relentless quest to find a cure for Nezuko, his sister who was turned into a demon thought she doesn't eat people. He is mourning over rengoku as he was there when it happened and looked up to rengoku. He is sad over he is sad over rengoku death.