Since there are certain risks involved in eating raw tuna, it would be a good idea for you to go to a restaurant or sushi bar where chefs who are properly trained in preparing and serving raw fish can provide you with what you want at a minimal risk to your own health. There are certain parasites, viruses, and bacteria that can grow on tuna along with just about any other type of raw fish which you will want to avoid altogether. Uncooked raw tuna can be dangerous to eat unless it is prepared and served by someone who knows exactly what they are doing.
Tuna is considered to be an oily fish and there are certain dangers associated with eating these types of fish, including dioxins and pesticides which can slowly start to accumulate in the body after they have been ingested. The accumulation and development of these toxins can lead to some serious health problems including toxicity which you will not want to deal with.
While it may be true that raw tuna can be eaten, it is important to consider some of the risks that are involved in doing so. Certain types of tuna can also contain high mercury levels, which is yet another reason why you will want to consider cooking it first and/or limiting the amount of it you eat so you do not risk mercury poisoning which can be a very serious medical problem.