Combine chicken, soy sauce, sake, ginger, garlic, sesame oil, and salt in a bowl. Mix well, cover, and marinate in the fridge for at least 30 minutes (up to 2 hours). Longer marinating tenderizes but don’t exceed 2 hours or chicken gets too salty.
Remove chicken from marinade, letting excess drip off (discard marinade). Dredge each piece thoroughly in potato starch, shaking off excess.
Heat 2–3 inches of oil in a deep pot or fryer to 340°F (170°C). Fry chicken in batches (don’t overcrowd) for 4–5 minutes, until light golden and cooked through (internal temp 165°F / 74°C).
Transfer to a wire rack and let rest for 5 minutes. Increase oil to 375°F (190°C) and fry again for 1–2 minutes until deep golden and crispy. Double frying ensures ultra-crisp exterior.
Drain on paper towels and serve immediately with lemon wedges and mayonnaise.
Additional Notes
Make-ahead: marinate chicken up to 2 hours ahead, dredge right before frying.
Use cornstarch if potato starch unavailable, but texture will be less crispy.
Add 1 beaten egg to marinade for juicier results (common home-style).
For variations, you can also make karaage out of pork loin, beef sirloin, squid, shrimp, or white fish.
Use a thermometer for oil temp. Too low and chicken greases up, too high and it burns.