Riding train. Saw this out of window, over mountains, close to sea. Matched speed of train. Disappeared behind clouds.

I was traveling home by train after finishing work in Himeji when I noticed an object in the sky. At first I thought it was a really shiny airplane but then I noticed it had no wings or tail. It appeared to be moving at the same speed as the train, at least from my perspective. There was only one object that day but after speaking with a friend recently, she mentioned seeing similar objects around our area. Unfortunately I lost sight of it behind clouds but I managed to take a photograph of it.