Bring the water and rice to a boil in a medium saucepan over high heat. Reduce the heat to low, cover, and simmer until the water is absorbed and the rice is tender, about 45 to 50 minutes.

Remove the rice from the heat and let it sit, covered, for 10 minutes — this allows the steam to finish the cooking process without the bottom burning.

Combine the vinegar, mirin, and sugar in a small saucepan and bring to a boil over medium-high heat. Once the sugar is dissolved, remove from the heat. Set aside a small portion of this mixture to season the rice, and whisk the soy sauce, ginger, orange zest and juice, and lime zest and juice into the remaining liquid to create the dressing.

Gently fold the reserved vinegar mixture into the cooked rice. Spread the rice slightly in the pot to help it cool while you prepare the toppings.

Whisk the cornstarch and cornmeal together in a shallow dish. Season the tofu fingers with salt and pepper, then dredge each piece in the cornstarch mixture, pressing firmly so the coating sticks to all sides.

Heat the oil in a large nonstick skillet over medium-high heat until it shimmers. Cook the tofu in batches until golden brown and crisp on all sides, about 8 to 10 minutes total.

Divide the seasoned rice into bowls. Arrange the crispy tofu, radishes, avocado, cucumber, and scallions on top, then garnish with nori if using. Serve warm, with the citrus-ginger dressing drizzled over the top.