What is the least rarest myachi?

Answer 1

Technically, there is no "least rare" Myachi, since all Myachis that are currently available on myachi.com have the same level of commonness, however, the most plentiful Myachi is the Sobe '02, of which 100,000 were made. Since this was last manufactured in 2002 it has since become relatively rare despite this high number. The Black Butter is also often referred to as the "Most Common" Myachi, since it was made in greater numbers than any other series (non-promotional) sack. Again, since it was last released in 2008, it should no longer be considered the "Least Rare" either.

The best answer to your question is that any sack offered in the 4.5 series is currently the "Least Rare".