Hmm, well Kasumi was only captured through winning the first tournament. They saw her as the superior ninja so they went for her DNA. The funny thing about this though, is that the final boss in DOA5 turns into all the ninjas. Which is weird since they should only have Hayate & Kasumi's DNA.... was that ever explained in the story? cause I still don't get it.
Free Step Dodge
FatalxInnocence
Animefreak40
I don't think it was explained in the story but ever since ayane got buffed she past Hayate, and Kasumis statistics in term of they re general skill but I think her buff put her on par with ryu . And since the boss in DOA5 turned into all the ninjas , I thought so too that ayane DNA was also collected but when 
? And where?
? And where?