Ichigo got blasted into past Gotei, 110 yrs ago, after defeating Yhwach. Trying to keep a low profile (but failed) but got ousted by Reiou (Soul King). After he killed Aizen or when he's still in the Academy, Ichigo would be called up in the Captain's meeting to step up because a member from the squad zero was asking for him. They want him to provide some of his reiatsu (due to its perfect combination of all races) for the Reiou, which he's already providing subconsciously. Reiou, awake and in his child form, would be there as well, clinging and shouting "Ichi-nii" to Ichigo. Ichigo would be his usual self (being impossible and super blunt, with a side of stubbornness/insubordination) acting as if that was all natural.