this sounds weird but what do I know

Kalanchoe.

I would second Kalanchoe. And this sprouting thing is very unlikely for really woody species, far more likely with this tender perennial.
You ever heard of " lucky baboo"? ( which is some kind of palm)

Bye, Lin

Several different kalanchoes grow plantlets along the edges of their leaves, but the majority do not. I don't know which type of kalanchoe that leaf belongs to.

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Lucky bamboo is certainly not a bamboo, but it's not a palm either; it's a dracaena, Dracaena braunii. This site has photos of several different types of dracaena:

http://www.bhg.com/gardening/plant-dictionary/houseplant/dracaena/

Most kalanchoes originated in Africa or Madagascar; some are native to Southeast Asia, but none to Japan.

I've read that one is native to Ecuador, but I'm not sure which one. It's the only New World kalanchoe, though several have naturalized in warmer parts of the U.S. and other parts of the Americas.

K. blossfeldiana makes a woody trunk but that leaf doesn't look quite right for that particular Kalanchoe. It does look/sound like some kind of Kal. In my experience playing with Kal leaves, it would be much more likely to not rot & successfully make babies if dry, not wet.

Looks like Kalanchoe pinnata to me. They can grow plantlets on the edge of the leaves.

Interesting to see the experiment this person did with leaves, at the link below.

Here is a link that might be useful: Kal pinnata experiment

Rosemarie, that's really cool, obviously I need to do more experiments. I will ask more about this on C/S. Thanks for the link & enlightenment!