Cut the chicken (600g) into ~3cm x 3cm chunks (you want them a little big, so they stay juicy).
In a large bowl, combine soy sauce (3 tbsp), mirin (3 tbsp), sugar (1 tsp), hondashi (1/2 tsp), garlic (1 tsp), ginger (1 tsp), and water (120ml). Add your chicken and gently toss together. Cover with plastic wrap and let it marinate in the refrigerator for 30 minutes or overnight.
Put the chicken in a strainer and let them drain.
Take out a tray and add a good amount of potato starch. Add a splash of water (about 2 tbsp), using a fork, mix and sort of press it down (we're intentionally adding clumps for extra crunch on the karaage).
Dredge each piece of chicken in the potato starch. Make sure you coat it all over and let sit on a wire rack for 5 minutes.
Heat up enough oil to cover the chicken to 170℃. Once it reaches the temperature, carefully add in your chicken and fry for 2 to 3 minutes. Work in 2 or 3 batches.
Once they get crispy on the outside, remove from the oil and let cool on a wire rack for 1 minute. Add your chicken back into the oil and fry for another minute or until golden brown.