Hitsumabushi is a local specialty of Aichi prefecture, especially in Owari region. Hitsumabushi looks like a typical grilled eel on rice eaten throughout Japan but it is different.
The first difference is that the eel is grilled but it is chopped in smaller pieces. Normal grilled eel on rice is not chopped in small pieces. The second way is way to eat. Ordinary grilled eel on rice does not come with small bowl and therefore you have to eat directly from the ware which grilled eel and rice are served. On the other hand, Hitsumabushi comes with small bowl for rice which you put the eel and rice from the bigger ware to the small bowl before eating it.
Then, the biggest difference is how to eat. Ordinary grilled eel has been grilled with special sweet but also savory sauce which is same to Hitsumabushi. However, Hitsumabushi comes with wasabi, chopped scallions ,seaweed, which are called YAKUMI - seasonings and soup. At first you should eat Hitsumabushi without any yakumi. Then, you should add the yakumi, which will change the taste. Then, finally pour the soup on the grilled eel and rice and enjoy eating it.
Although western steak or French fries are eaten with sauces, ketchup and mayonnaise, you can not change the principle taste of the meal. Normally you will add either ketchup or mayonnaise to the fries. However, Japanese cuisine is different. Many meals can be enjoyed in several ways also during the meal.