Ok, so a friend linked me to the Japanse wiki and I found somethings out.
Let's start with these 4 bosses that are shown in the picture on the Aeria forums.
A friend and I have figured these to be elements (Sui = water elemental, Fuu = wind, etc)
This guy seems to be named "Kinki."
Weaknesses: shock, magic, spirit and nerve
Resistance: physical proximity, gun attack, demons destruction
Disabled: killing curse , lightning
Reflection: n/a
His name is apparently "Suiki" and he's an ice type, I believe.
Weaknesses: fire, magic, nerves, mind
Resistance: Magic fracture (??)
Disabled: freezing and killing curse
Reflection: n/a
"Fuuki", a wind type.
Weaknesses: Lightning, Magic, nerves, mental
Resistance: Magic fracture
Disabled: killing curse
Reflection: Impact
"Ongyouki." We're assuming he's a death elemental.
Weaknesses: Magic fracture
Resistance: n/a
Disabled: All Physics (?), killing curse, witchcraft (?), spirit
Reflection: n/a
After some research, we're assuming these guys are in reference to the anime "Requiem from the Darkness."
Here's a quote from wikipedia. "The three spiritual beings are recurring characters in the show who function
as a team that punishes sinners who emit a dark aura about them, most frequently murderers. To that end,
they use their talents to set their target up to face his crimes before being executed and committing them to
the next world." In other words, the elementals are the spiritual being, and Ongyouki is the judgment.
I'm too tired to put more, so enjoy ^^