Onnen Musha is the weakest of the three Mushas in Empyrean, with HP less than a third of its counterparts. However, it makes up for this by being immune to non-physical elements, forcing the player to power through it with physical attacks or spend turns on Break spells. It has several physical skills and a slight focus on Poisoning the party if not trying to kill them with a boosted Mamudoon. Focus on defeating this shadow first to minimize the Poison damage that would be taken during the fight.
The Raindrop Musha reappears in B5F and B6F of the Secret Laboratory within the Midnight Channel on rainy days. It will use Balzac on itself to raise its attack power, but this will also make it more vulnerable to attacks. After being defeated, it may drop the Rain Metal material. Selling a Rain Metal will unlock the Amamusha Armor for males in the shop, which has the highest equipment rating for male armor available from the Secret Laboratory and a Resist Dizzy effect, but also has a very low Evade stat.
In Golden, it appears from B5F to B8F. It may also drop Meteorite, Rose Quartz or Buffalo Stone for trade at Shiroku Pub.