Put the Sake, sugar, and clams into a large frying pan and stir together. Bring to boil over high heat and cook for 3 minutes, uncovered. Stir in the Soya sauce and cook briskly for another minute. Remove from heat and set aside.
Boil the remaining liquid for 10 minutes until it becomes syrupy. Add clams and stir them gently in the sauce over hight heat for 1 minute.
Transfer to deep bowl, and cool to room temperature. Serve cool.
NOTE: Tiny Shrimp, mussels, or bits of fresh tunny fish may be sustituted for the clams and cockles.