If you take a taxi ride in some Japanese cities, you may see advertisements featuring Junko Kubo, a former female anchor on Japan's public broadcaster NHK. The ads simply read: "Government bonds are worth another look."

This is not the first time Japanese government bonds have made it to ads and billboards. As early as 2005, Japan's Ministry of Finance decided to promote its bonds. But when a big buyer has finally emerged now, many Japanese media outlets and individuals don't seem to welcome it.

According to Tokyo's latest official data, China purchased more than 1.73 trillion yen ($20.1 billion) worth of Japanese bonds in the first six months of this year. That's a giant leap compared to the past: almost seven times the one-year record of 253.8 billion in 2005. And it makes China the second largest creditor to Japan.

But China's purchase actually has little impact on China, because the Japanese bonds make up a tiny proportion of Beijing's foreign exchange reserves: less than 1 percent of the total $2.45 trillion.

In the international bond market, Japanese bonds are not hot stock. Low interest rate and lack of liquidity have long made them unattractive to many buyers, including China. Though no official data is available, many scholars say the combined US dollar assets comprise most of China's foreign exchange reserves, while its assets in Japanese yen make up a tiny part.

Perhaps that's why this purchase has drawn the world's attention. Many Chinese economists are analyzing the gains and risks involved in buying Japanese bonds. And some Japanese doubt the real intentions of China in buying their country's bonds. One Japanese netizen even wrote an article: "Will Japan be fooled by Chinese hot money?"

Yuan Changjun, a research fellow in finance with the University of International Business and Economics has analyzed the advantages and disadvantages of purchasing Japanese bonds, and suggests China could increase some of its Japanese bond holdings in order to diversify its foreign exchange reserves.

Risk is always the first factor to be considered while making an investment. Many people have expressed concern over security, for Japan has the largest public debt among industrialized nations. According to the International Monetary Fund, its debt had reached 218.6 percent of its GDP last year, much higher than the 113 percent of Greece. Even Japan's new Prime Minister Naoto Kan has warned of the possibility of a financial mess, fearing it could turn Japan into another Greece.

But Yuan says the risks of Japan going bankrupt are not so high. Unlike the assets of the US and European nations, most of the Japanese bonds are held domestically. Foreign institutions and individuals hold only 4.6 percent of the total, while the percentage of British assets held by foreign entities is more than 30, and even above 40 for the US and Germany.

In fact, Japanese financial institutions have kept good their credits, with only a few uncollectible accounts, giving the country a firm financial footing, Yuan says. Besides, Japan has got enormous overseas assets, which add security to its debts.