In a large bowl, place the drained tuna, radishes, shredded carrot, garlic, ginger, chili, vegetable oil, dark sesame oil, and rice vinegar; gently toss to combine.
Add salt and pepper to taste.
Refrigerate until ready to serve.
When ready to serve, stir in the chopped cilantro and green onion.
Serve with lettuce, or mixed in with cold, cooked soba noodles.