Slice eggplant into 1/4" slices, leaving skin on. Sprinkle with salt and set aside for 15 minutes. Wipe off moisture.
Lightly coat the eggplant on both sides with starch.
Heat 2 Tbsp. oil in a pan over medium heat. When shimmering, add eggplant in a single layer. Cook undisturbed until bottoms are golden.
Drizzle remaining oil over eggplant, flip, and cook other side until golden.
Reduce heat to medium-low, add mirin, soy sauce, and ginger. Return to a simmer, basting eggplant occasionally. If sauce becomes too thick, thin with some water. Remove from heat when eggplant is well coated with sauce.
Serve eggplant over rice in a donburi, drizzled with sauce and garnished with shiso and sesame.