i DON'T KNOW WHAT HOSOKAI IS USING FOR BLOODLINE. But I have watched him over the last 10 years really do a good job of breeding many color varieties after solely being known for asagi.
the koi's sumi to me is typical matsunosuke. It is true they grow long the first 3-4 years and then bulk. Most of the better koi of this bloodline take 7-8 years before you really know what you have from a quality/body shape standpoint.
I think another breeder, known for his shiro utsuri has done a marvelous job
of breeding kohaku and showa....Omosako.
I think knowledge of a bloodline is helpful but to much emphasis on a name can hurt your ability to recognize a truely good koi irregardless of who bred it....