After winning the battle on the beach against the minor Boss that resembles 
a giant crab, and can
move onward to the next area; save the game but do not proceed ahead. 
Instead, backtrack to the
beach and defeat the enemies modified with the Mashogane. They do not stop 
respawning .and will
provide a limitless amount of Mashogane to boost your weapons attacks to 
their maximum at this
point. Kill off a good number of them, then when a large number of enemies 
are present use your
Kamui to take them out and reap in the benefits. This may also give you a 
healing item such as a
Miracle Pill or Tengu Herb. Also, retreat back to the save point whenever 
your health gets low.
Do not use your healing items as you will need them for the Boss fight that 
is just past the save
point near the Soul Gate.