What are the Pain's theme song lyrics?
Long shot, guys, but don't you think that if it's a chant it can be in Chinese?
For example like this:

没师傅你哭吗    Méi shīfù nǐ kū ma
那你可那波苦    Nà nǐ kě nàbō kǔ


First two lines can be then read as such:

Master didn't cry for you
You can wave of that pain


Then I'd go with Japanese/English line:

いけない FORGIVE    Ikenai FORGIVE


And that one means simply:

Don't forgive


The only thing I can't possibly get is the last line... It sounds Latin-ish, but it can't be as there are no words fitting phonetically to these syllables...
It sounds between Japanese and some ancient European language...

What do you think, guys?