Sushi is tasty and healthy food. It's been around for a longgggg time, but only during the last 20 years has become an adventure for Americans, due to our people who went to Japan for business, and found a love for sushi when they tried the Japanese cuisine. Soon enough people wanted it, and as you know, "if you build it they will come!"
People who have a sensitive palate, and genuinely want to expand their eating experience will like sushi. Those who don't like it seem to be unable to get past the mental image of eating a cold uncooked fish. The other related issues are that the fish must be very fresh, the rice should be slightly sticky and not cold, the rice must be properly seasoned (it isn't just plain rice), and the sushi must be freshly made, (not pre-made and kept in a cooler like so many markets do).
Sushi is made in small, bite-size components, because it is intended to be handled with chopsticks. The pieces are served with soy sauce, and dipping the sushi pieces in it make the food much more palatable. Adding some wasabi (a spicy green horseradish) will add some zest to the taste.
Roll sushi comes with sliced fish, or sliced cucumber, or other items rolled in a layer of rice, and wrapped in nori, which is a refined seaweed. Fish sushi is a small slice of fish laid on a pat of rice. All of it is great. My favorites are smoked eel, salmon, mackerel, and giant clam.
Go with your friend, without any hang-ups, and look forward to something special. Like so many who have already posted here, I think you will like it.