It's just a guy who thinks everything he doesn't like must be purged even if there's no reason to remove it.
Nah, I understand people that don't like seeing guro, especially not on this site. I was reluctant to post any of yaruku's bloody stuff for a long time now, like this images is 2 years old. Despite how upsetting they were at the start, yaruku's art is pretty special and sekibanki's antics grew on me. Kogasa's solo stuff though just seems gratuitous, I'm not touching those.
What in this image proves that that girl was Kogasa?
1 year later: We know it's Kogasa from her pixiv solo series done by this artist. There, she gets a barcode tattoo in the same place as it appears in this image. + there are some other related actions in that. FJH reasoning is also good, the umbrella was a nice touch.