it's not peach.. Perhaps.. It's you.. It's been years since Kaigaku haven't talked to you, you we're both former lovers.. And now it's ex-lover, In the hashira training arc,you also received the letter which is also said that the former thunder hashira Jigoro Kuwajima died due to seppuku, timeskip, at night, you got teleported inside the infinity castle, then you encountered Kaigaku which he's a demon now