I think the title is a multiple-reading joke. As written on the first page, it reads 石 コロ殺意.
石: ishi --> stone/rock
コロ : ko ro --> around/near/toward
殺意 : satsui --> murderous intent/impulse
"Murderous impulses near rocks!" A tale of one girl's passionate, violent pursuit of another girl through stone pits that ends with both in a cement mixer that ends messily for all.
Yuri fury lures quarry into gory quarry slurry!
. I APOLOGIZE FOR NOTHING! .
... cough ahem ... Sorry, I don't know what came over me.
Back to the title. Group the "ko" with "ishi" to get "ishiko" or "stone girl." Or, "ishikoro" could be short for "ishi kokoro," which is "stone heart." So, the title might be something like "The Urge to Kill Her Stone Heart."