The Japanese smile is not necessarily a symbol of happiness or acceptance as in western culture. The j-smile can imply everything from sadness, embarrassment, confusion or that they “don't know”.
The j-smile is a powerful act in the silent culture of japan, where avoiding conflict and confrontations is essential.
Japanese even have developed a camera with smile recognition software, which snaps on the trace of a smile.

The Japanese smile takes its cue from the days when Samurai women were required, like the women of Sparta, to express joy on hearing that their men had perished in battle. To betray any sign of sorrow was a serious breach of their code of honor. Japanese greetings occupy the whole face, head, and torso, which are tilted toward the other person, a display reminiscent of the old fashion shopkeeper's or salesperson's smile to signal, "I aim to please."

There is a gamut of emotions that a smile conveys in other cultures. In Indonesia a smile may denote either happiness or anger, while the Thais, Chinese and Koreans will smile to express their confusion, embarrassment, or even sadness.
In many lands, Sri Lanka, India, the Gulf States, and many nations in North Africa, smiling at a member of the opposite sex is taken as an invitation to flirt or have sex.