Combine tuna, chives, sesame oil, soy sauce, vinegar, salt and pepper in a medium bowl. Cover tightly and refrigerate. Mix the mayonnaise and chili paste in a small bowl, cover and refrigerate. Slice the cucumbers lengthwise, as thinly as possible into approximately 5-inch lengths. Season with salt and pepper to taste. Place 1 heaping teaspoon of the tuna tartar on one end of the cucumber slice. Roll up. The cucumber, when very thinly sliced, will stick together and stay rolled without a toothpick. Continue making rolls with the remaining ingredients.
Top each roll with 1/4 teaspoon dollop of spicy mayonnaise and a sprinkling of sesame seeds.