Pound chicken breasts until even thickness and season with salt and pepper.
Dredge each piece in flour, dip in beaten eggs, then coat with panko breadcrumbs.
Heat oil in a pan over medium heat. Fry chicken until golden brown and cooked through, about 4 minutes per side.
Drain on paper towels and slice into strips.
Pack bento boxes with rice, shredded cabbage, pickled vegetables, and sliced chicken.
Drizzle with tonkatsu sauce just before eating.