Bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally, until tender yet firm to the bite, about 12 minutes. Drain, reserving 3 tablespoons of the cooking water.
Heat 1 tablespoon olive oil in a skillet over medium-low heat. Cook and stir red bell pepper in the hot oil until softened, about 5 minutes. Stir in okra, soy sauce, sake, and mirin; cook for 1 minute.
Stir cooked spaghetti, reserved cooking water, and remaining 1 tablespoon olive oil into the skillet. Mix in half of the shrimp; cook for 1 minute.
Scoop spaghetti mixture into a bowl. Garnish with remaining shrimp.