Doors
In Asia, it's generally believed that a person's soul will become a ghost if he/she died with a strong wish unfulfilled. This "wish" can take the form of a desire, a worry, or a strong emotion.
In the world of Shaman King, this belief also exists (editor 262501: what a rubbish sentence!) but with the additional explanation that 'ghosts' are a type of 'oversoul' which only people with shamanic power can see and are generated with quantifiable energy called "Furyoku", which can be roughly described by the strength of a thought.
Many Asians also believe that a ghost will "become buddha" when the 'wish' which supports the ghost's existence is fulfilled/eliminated, and he/she no longer has any regret/worry.
Therefore in the manga of "Shaman King", the guy which dropped dead from the ladder he was sitting on when he was painting a billboard became a ghost and tried to hurt Manta because he didn't know he's dead and he wished to finish the advertisement he was painting. Yoh let the ghost possessed him and finished the painting and then the ghost 'become Buddha'.
In this Scene, HAO became buddha became his wishes -- to be accepted as who he is, to live a happy leisurely normal life etc -- are fulfilled and that he has no worry -- seeing the one he loves, Anna, obtaining "SHIAWASE" (something like bliss), and that his brother are carrying out his responsibility of being the Shaman King properly and happily, and he no longer regrets his 'crime' -- he had repaid them by helping Yoh greatly with his responisbility of being the Shaman King, as well as being killed and then being the primary spirit of Anna for several years (no one would think it would be an easy life to be the primary spirit of Anna, right?).
Doors
Back to Scene 25 (English translation) of Last Episode of Shaman King
Door to the Corridor of Shaman King in MESSWORLD
THANX TAKEI!