The god worshipped by the character Hidan from the show Naruto. It means "evil god" or "evil heart". Jashin, according to Hidan, expects that all followers of Jashin bring nothing less but utter destruction and death. Always before a fight, Hidan prays to Jashin, asking for a "good kill". If he is unsuccessful, or is not allowed to kill, he prays for forgiveness.
Jashin will punish you for not watching Naruto!