Hello,
I'm new to this forum but i'm reading the posts here for several years now. As i'm collecting Hippeastrum i have a bukasovii hybrid, too. I didn't acquire mine directly from Komoriya but from a reseller on ebay as a small offset. After feeding it well for a little less than a year, it flowered for the first time in my greenhouse last summer.
I think mine has definitely simmilarities to yours but there are differences too.
The colour for example is pretty similar to yours but mine has a completely different shape with much narrower petals.
So i wonder if it's just the natural variety of this clone, if several siblings of this cross are sold under the same name or if i have something completely different.
Regarding the parentage of this plant i don't really have a clue but H. yungacense as you mention could definitely have been involved.
Now for comparison a picture of my bukasovii hybrid:

{{gwi:2122431}}

Best regards,
Dominik