Not much to it.
That was more a teaser than a trailer. There should have been a tad more to it, like more unveiling of story or plot. Your visuals were alright, you might want to work on limb animation if you haven't already; it really makes your characters come alive. The audio was pretty cool, catchy and it didn't make for a huge filesize. The style is somewhat lacking, since it was so short. This vaugely shows that there's some pacifist place with some different boy. Looks like it could be ok, I would have needed to see more to get a better impression. Hope you'll keep working on it.