Tsurubami isn't on vacation at all
Word of God heavily implies there will be stronger characters than Tsurubami appearing in the future. Whoever these characters may be, chances are they disapprove of their dictatorship over Mugenri as much as the next person (or possibly something else behind the scenes). The biggest difference is that they're willing and able to do something about it. Tsurubami was able to know about this far ahead of time, and so formed a plan to spirit away someone who looked like them to take their place while they pulled a Karma Houdini. Monochrome World will be a Megaman clone
JynX describes MW as being a "2d action game", which in Japan usually refers to action platformers like Megaman.