Ichigo watched as his zanpakutō shattered after the mortal battle with Yhwach and his minions. Nobody at Seireitei seems to be able to fix Zangetsu is the protagonist's only hope bleaching appears to be Captain Nimaiya of the Zero Division, the Royal Guard protecting the Royal Palace.
In Bleach: Thousand-Year Blood War 1x10, Nimaiya refuses to fix Zangetsu as Ichigo is not a worthy Soul Reaper as he was not chosen by any Asauchi. Banned from Soul Societythe deputy Shinigami is forced to return to the human world.
In the eleventh episode of Bleach: Thousand-Year Blood War, Ichigo suddenly finds himself outside the family hospital, but before his father can welcome him into the house, he runs away to seek refuge with Ikumi. However, his father soon joins him and confronts him with the facts. Ichigo thus discovers his pastbelonging neither to soul society nor to the human kingdom.
Through a flashback we go back to the time when Isshin Shibai was the captain of the 10th Division of the Gotei 13 and Hitsugaya his third seat. Captain Isshin is informed of the deaths of some Soul Reapers and decides to embark on a solo mission to the human world.
Meanwhile, the true story of Masaki KurosakiIchigo's mother. The woman was one Thoroughbred Quincywelcome to the Ishida house as the fiancée of Ryuken Ishida, Uryu's father.
Isshin located the Soul Reaper killer, which turned out to be a Black Hollow freed by Sosuke Aizen, Gin Ichimaru and Kaname Tosen. However, during the battle he was treacherously wounded by the three, hiding in the darkness, only surviving thanks to the intervention of Masaki, who rushed to the scene of the battle after noticing the captain's reiatsu. So that was the first meeting between the Shinigami and the Quincythe future parents of Ichigo Kurosaki.