Wash hijiki seaweed well in ample water, letting sand and unwanted particles sink to the bottom of the bowl. Scoop hijiki out with strainer. Soak hijiki in lukewarm water for 30 minutes. Rinse again in water and drain well.
Cut chicken into 1cm pieces. Heat oil in a skillet, stir fry chicken then add the hijiki to warm through, then serve.
Add all sauce ingredients and cook over low heat for 15-20 minutes, until the sauce is almost gone. Serve immediately.