From eManga:
When the meanest, orneriest, no-good black hat, known as the melon kid comes into town up looking for trouble, the townsfolk look to their sheriff, the famous civil war hero, the lemon kid to protect them. With the deadline to get out of town looming, can the two anagramic gunslingers overcome their shared history before it ends in a shoot-out?

Bonus story: in a bid to find a trade route linking the east and western united states, can the intrepid members of the 13th expeditionary party make it through the dreaded black canyon alive?