Mana Kitazawa was 18 months old in September 2004 when she first started going to Poppins International Preschool in Shibuya Ward, Tokyo.

Now she sometimes talks to her parents in English.

"We talk to her in English only when she voluntarily talks to us," said Tomohiro Kitazawa, who works at a foreign-affiliated company. He and his wife, Sai, lived in the United States for a few years as university students. "About 15 to 20 percent of our conversations with Mana are in English."