Arajiru is a fish soup using ara = fish head, bones, gills and flippers; leftovers of fish when making sashimi. The soup contains also other ingredients such as vegetables and konjac.
The soup can be clear soup or miso soup. In case it is clear soup, salt or soy sauce is added. Due to ara contains bones, usually broth is not needed to make the soup. Ara is usually from large fishes, such as greater amberjack, seabream or amberjack. Tuna and salmon are not common as above fishes but also can be found in arajiru.
The portion of the soup is usually bigger than ordinary miso soup which comes together with meal at the diners and therefore it can be considered as main dish too. However, the price is kept low due to using leftovers. Then, arajiru can be found at diners located at fish markets or restaurants which offer various sashimi or sushi.