日本至7月4日当周买进外国债券 16568亿日元，前值1828亿日元。

Group 1 - The core point of the article indicates that Japan purchased foreign bonds amounting to 1,656.8 billion yen in the week ending July 4, a decrease from the previous value of 182.8 billion yen [1] Group 2 - The current foreign bond purchase reflects a significant drop compared to the prior week, suggesting a potential shift in investment strategy or market conditions [1]