(not complete yet) I remember seeing at least 6 of the raw chapters available for purchase on a website a while ago. I can't remember what site, but I can confirm that the uke is a horse beastman instead of a full-on horse. So if you're concerned about a man fucking his horse, let me inform you that the man on the cover only fucks his horse when both are humans. The story starts with a man riding a horse only for it to end with him getting the horse to ride him. ;)
Shouwaru Boukun Kishu to Nagasare Senba