The spell used by Souji that is referred there that he used on Izanami is Ikuman Shingon, which roughly translates to Ten Thousand Truths, possibly a counter to Izanami's Thousand Curses.
I'd love to think of this as an Alternative True Ending... Ending a grudge of a few thousand years, two deities are reunited..
I am convinced someone on the P4:G team read this comic.
what with Marie being Izanami and all
What a miracle--No way... what--With this, it's finally over.I came to meet you.I will look at you, gazing at you from my true face.Killed by you again... not bad.
Please... end this long, long journey.Don't make decisions like passing on by yourself anymore!I've been subjected to Myriad Truths, yet... I still exist?