In old Okinawa, Japan where banana plants were once flourished forming large piece of banana jungle; night travelers passing through this banana forest would come across this type of spirit. Having said so, the belief of banana spirit is not native to Japan.
There are stories told that when beautiful girls passing through banana plants at night, they would come across very handsome young man. These girls would then conceive and give birth to 'ghost baby'.
The locals believed that one must bring along sharp knives to protect himself/herself when passing through banana plants at night or facing the risk of being attack.
In some places in Japan, people still believe a banana plant brings bad luck and causing sickness. Some Chinese also holds the belief that banana plants attract yin-energy so they are not suitable to be planted near the house.
It is a little different with Japanese, Chinese believe that a banana spirit normally shows itself as a pretty lady enticing lustful young man to mate with it. If the spirit is satisfied, then the man can be rich with the help of this banana spirit. But the downside is that this person may die of life energy depletion over time.
There are many rituals meant to call out a banana spirit at night to ask for favours:
Folklore described that when a banana plant flowers, its bud should be tied with a piece of red string on one end, and the other end of the string is tied to the toe of the person who wishes to summon banana spirit.
It is said that a beautiful lady will come to the person and satisfy his lust.
Other ritual said that one should get a pair of iron scissors and stab the scissors into the banana trunk. Then a piece of the red string is tied to the handle while the other to the person's toe.
This later method is a more powerful way to force the spirit out. But the person must remove the scissors from the trunk after the spirit has done what is required or very bad consequences may entail.
It is also possible to ask lucky numbers from banana spirits. One only need to write a series of numbers on some small flags. Then all these flags are plugged under banana plant at night. In the next morning, the topple flags would indicate the choice of numbers given by the banana spirit.
In Vietnam, some men would look for banana plants near rivers and bring the banana plants to his house. This is known as 'marrying a banana plant'. Such action is believed to bring luck and fortune to a poor man. This man must treat this banana plant as his lawful wife.
Banana spirit is depicted as Phi Phop in Thailand and amulets of banana spirits are sold as lucky charms... The Thai banana spirits are believed to dwell in wild banana plants outside a village. You will see some sort of flower garland hung on the trunk when you visit Thai villages. Banana spirits are only revered by the Thai than having romantic thoughts however.
Of course, the level headed westerners have no such sort of fantasies as the Asian!