Totentanz Riddle 9

Now seriously:

U = Ushio 
M = Misako
N = Nami

BM = bad mermaid
GM = good mermaid
H = human

1. U is BM, M is GM and N is H
U lies saying that M is a mermaid
WRONG

2. U is BM, M is H and N is GM
U lies saying that M is a mermaid 
RIGHT
M comment is ignored
-

3. U is GM, M is BM and N is H
U says that M is a mermaid
RIGHT
M lies saying that M is a mermaid
WRONG

4. U is GM, M is H and N is GM
U says that M is a mermaid
WRONG

5. U is H, M is BM and N is GM
U comment is ignored
-
M lies saying that U is a mermaid
RIGHT

6. U is H, M is GM and N is BM
U comment is ignored
-
M says that U is a mermaid
WRONG

Check again and you will notice there are only two posible answers

2. U is BM, M is H and N is GM
5. U is H, M is BM and N is GM

In both cases Nami is the good mermaid

Are you impressed? because I do.