i heard a myth that some Japanese bullet trains go so fast that if one was shot while riding by a shooter in a stationary position, that they will be able to survive (albeit with some injuries).

Depends. I don't know the exact speed of a typical bullet train but I wager somewhere in the range of 300-450 fps. That is a considerable chunk of a bullet's velocity, but it's purely up to chance and a good bit of luck whether it will be enough to leave you alive when you'd otherwise be dead. If the round is a standard pistol caliber, say .45 ACP moving at 900 fps (pretty slow for any round), then you've effectively removed a third to a half of its velocity. Could be enough to make a difference, depending on a number of things.

With any centerfire rifle, forget it. Won't matter.

Ya but dude I don't know about that cause Ive never seen a "bullet" train going as fast as an actual speeding bullet. But that would be so cool to reach out and grab a bullet flying right beside the train. Hm........

A Bullet train has a speed of around 200mph, but would the speed of the train relly make that much difference?
WWII fighter planes Spifires,Me109,P51 Mustangs all flew more than twice as fast and many, many pilots were killed by enemy Guns.

Yes but relative to the planes' velocity the bullets were going the same speed as they would go on the ground. The OP is talking about someone on the ground shooting at a bullet train that is moving away from him.