Did the father thunder god make it so he looked like a female oni to other oni in hell? That's a fitting punishment if true.
Kind of a bittersweet ending for a story that easily could have gone on longer. That blue "omake" page at the end proves that they had children, or at the very least one, and she's still as happy as ever with him being old and gray. Does that mean his kid(s) are part raijin as well?