I don't quiet understand the terms IR said 'Ychwach would comeback and kill Ichigo in the happiest moment of Ichigo's life' and assuming it's when Ichigo and Rukia meet again because Ychwach appeared in the manga panel when Rukia and Renji came to visit them in Karakura Town. Is that assumption true? Since Ychwach wasn't fulfilled his goal to kill Ichigo when he married Orihime, or when Kazui born.
It isn't about Ichigo seeing Rukia again being his "happiest moment." In Yhwach's speech, he's speaking to all of them as a group, not just Ichigo. He says, "I shall leave this gate open for all of you, if any of you do choose to pass through...and I shall find that one moment in the future where each of you feels the greatest amount of joy and happiness." (Link) (Link) It was about all of them, in a moment when they were happily together and reunited in the epilogue.
But I think people also forget the logistics of it. Kubo said he always planned for the final chapter to end with Ichigo's son meeting Rukia's daughter. So, if the final chapter had Yhwach reappearing at Ichigo and Orihime's wedding, Kazui wouldn't have been born yet. If he reappeared the day Kazui was born, he would have been an infant and therefore too young to actually meet Ichika (or for the readers to really "meet" him and gain an understanding of his looks/personality). It was necessary for the final chapter to be enough years ahead in time to really catch up with the main cast in an epilogue fashion and give them all that "greatest joy" moment, and for Ichika and Kazui to be old enough to meet (and for the audience to meet them, as well).
Yhwach first came back around Ukitake's grave in chapter 685 even before Rukia's captain promotion ceremony, tell them to explain that lol.
Also, Yhwach promised the people who would cross the portal to find the moment where they feel the most happiness and kills them there, the people who crossed are Renji and Ichigo, when Yhwach came back he was nowhere near Ichigo and Renji, he appeared in front of Ichigo's son Kazui and not in the living room where Ichigo and Renji were located, Yhwach was going after Kazui, so tell them to explain that too.
I know some of them really struggle with reading comprehension, so we have to spoonfeed them information or else they drown in headcanons and fanfictions like they always do. I mean how can someone ignore the fact that Yhwach came back in chapter 685 around Ukitake's grave first even before Rukia's captain promotion ceremony and the whole Chad watch party thing, and why do they act like Yhwach was about to kill Ichigo at his happiest moment meanwhile Yhwach appeared in front of Ichigo's son and not around Ichigo, clearly going for Kazui and not Ichigo. lol














