Ochinchin is a word used by young Japanese children, mostly boys, to refer to a penis. It's usually used in an innocent, teasing context. In true shota, it is used a lot.

Large, beautiful breasts that are keep well consealed and initially appear to be much smaller and less impressive than they actually are until unleashed.

A slang term used by children in Japan as a replacement for the word "Penis" (like in america "willy/weenie")