User blog comment:Godisme/Everything But The Rain Op. 3 Dark of the Moon/@comment-4957813-20130313210833/@comment-1055570-20130313214831

No. The hollow that appeared just has huge similarities to Hollow Ichigo. My theory is since it says at the start of this flash back that Masaki killed something, I'm going to assume it's this and she absorbed it's Spirit Particles either knowingly or unintentionally (since quincies can do that) and they passed onto Ichigo when he was born. Might explain why Aizen was so interested in him, even from birth.