In the past, I have seen strange things in the Tokyo sky, mostly things that looked like balls of plasma meandering about. I didn't think to report those because I felt that they might be natural in nature (example: ball lightning, or something related to our earthquakes). This however was different and definitely not natural. This time they were craft. Two of them, shaped like crescents, boomerangs, a "V", or however you want to call it. Half transparent, no lights, no sound, and traveling around 2500 kph. by my estimate. Though they had no lights, they were visible from ambient light from Tokyo. They seemed somewhat transparent. The same way that a small lone cloud is visible but also transparent looking in an otherwise crystal clear night sky. January 5, 2013 around 6:10 pm, my wife, my son,and I were coming home from dinner. The sky was super clear and many stars were visible (rare for Tokyo). As my wife unlocked the door to our apartment, I was enjoying the wonderful view of Jupiter. That's when suddenly the two craft entered my field of view. One was traveling to the East/Northeast, and the other was traveling to the East/Southeast. Their trajectories and positions in the sky were perfect intersecting mirror images of each other. When there positions had reached a distance from each other of about the width of six to eight of their craft, they went into formation flying east for a moment then banking hard to the right, quickly flying out of sight to the Southeast. The whole event lasted about 5 seconds. That's how long it took for them to traverse the entire sky at a what appeared to be an altitude of around 5000-8000 feet, assuming they were just a little larger that commercial aircraft. Of course, size, altitude, and therefore speed were hard to judge as there were no clouds. I don't think that a living being, at least not humans, can survive the G forces that these craft had to be enduring. It has caused me to see my other sightings in a different light now, so I will be filing reports on them as well, although some were quite a while back.