Nice, but you aren't Japanese
I'm living in Japan right now, and while nothing was really wrong with this animation, your accents REALLY need work. The fact that this was done by Americans or some other non-Japanese group was painfully apparent.
In Japanese, the vowels are solid as all hell. Your speech is too relaxed; it sounds definitely un-Japanese. Make all of the sounds more solid; in Japanese, people understand each other perfectly despite the ungodly speed of their speech, and the definitiveness of all of the syllables is what allows for this to happen.
I personally think that you should keep it in English. However, I'm a rarity living in Japan, and I remember thinking how charming it was that this was in Japanese when I watched this back in the states.
Nice work overall. The (to the high-standards me) bad accents knocked it down two points, in addition to the lack of eye-coordination on some of the characters (the scientists were REALLY bad about this). Another thing that bothered me is that, while the artistry is good, the animation is jerky, and I'm not talking about performance and framerate. Simply, more drawings need to be done. Look at Mousekliks' work if you want an example of Godliness. His accent for the voices in FFA+ is really good, too.
Fix all of these issues, and you'll have yourself a GODLY flash. I'm giving this a 5/5, and an 8/10. Nice work!