Sumo and smiles ¡ª two words that rarely go together.

Japan¡¯s national sport is famous for the stoic seriousness with which its participants conduct their affairs both inside and outside the ring.

Whether it¡¯s refraining from showing emotion after wins to giving boilerplate post-bout interviews about taking everything one day at a time, professional sumo wrestlers have to adhere to one of the sporting world¡¯s strictest codes of conduct.