Compared to the previous bosses in Empyrean, the three Mushas are relatively straightforward, without a complex mix of resistances or Evade skills. All three, however, can throw around Mahamaon and Mamudoon, so bring along Personas that resist both Light and Dark to avoid an unceremonious end to the battle.
Tenjin Musha is the most durable of the three, focusing on physical attacks and supporting the rest of its party with buffs and healing. It would be best to focus on taking down the other Mushas one at a time instead of throwing around spread attacks which can be buffered with Mediarama, or to focus on the Tenjin Musha to remove a source of buffs and debuffs.
Rain Wind Musha is found in the 8th and 9th Paradise of Heaven within the Midnight Channel on rainy days. It is solely a physical attacker, dodges physical attacks, and cannot be dizzied. In addition to repelling or draining elemental spells, it slightly reduces damage from Physical attacks and Almighty, but it's three times more likely to be hit with Light or Darkness skills. Rain Wind Musha will alternate between physical strikes and Power Charged strikes. Upon being defeated, it may drop Cascade Metal. Selling the Cascade Metal at Daidara will unlock the Ame-agari Kesshi male armor in the shop.
In Golden, it appears in Paradises 3 to 9 of Heaven. It may drop Sphalerite, Aurora Stone or Sunstone for trade at Shiroku Pub.