It was the summer of 1997, my first time in Japan. My father had arranged for me to stay with his friend in Kumamoto — a doctor who ran a small hospital. His family made me feel welcome right from the start. One morning, I wandered into the kitchen and saw a bowl of leftover rice from the night before, a pot of green tea, and these small paper packets on the table — the kind you get at the supermarket. The doctor’s wife tore one open, sprinkling its mix of dried seaweed, tiny rice crackers, and powdered seasoning over the rice. She poured in the tea and passed the…