SD Gundam: Musha Banchou Fuuunroku

The 17th installment in the Musha Gundam series.

Official relations were formed between Earth and the land of Ark. At an inter-racial school attended by humans and Mobile Citizens, young Ryuunosuke befriends fellow student Kokuryu. Life at the school can sometimes be fierce, with student gangs seeking to disrupt the harmony. But in the face of this, Kokuryu reveals a powerful ability- although he normally looks like a little kid, he can transform into the maturer samurai warrior Kokuryu Gundam.