User blog comment:Xilinoc/Ch. 686 - Death & Strawberry (End of Bleach reMIX)/@comment-1489595-20160819152958/@comment-5398287-20160820221602

Difference between Ichigo/Rukia and Isshin/Masaki is that Masaki was flirting with Isshin very quickly after she met him, whereas in the 2 in-universe years of Bleach, Ichigo and Rukia never once displayed anything other than platonic affection for each other.