User blog comment:Xilinoc/Ch. 659 - There Will Be Frost/@comment-11446176-20160122075311/@comment-5398287-20160123002236

The theory that I find most likely is that he was autopsying Katagiri's corpse for so long because of how she died: she dropped into a coma for three months while in regular health and then died, and Ryuken had no idea why, so he kept searching for a cause of death long after he did for most dead people. It's kinda sad, really, especially with that look in his eyes.