👀 Mind if Kōtarō shoots his shot for interaction ideas...?
Interaction Ideas
I'm going to be honest; given that Yamamoto considers even Lieutenants expendable, I don't think he'd give those who are Fourth Seat or lower during his life the time of day normally. So this is going to be one part contrived and two parts cheating. With that said, here we go:
It is the day of Kaien's death. Yamamoto visits the 13th Division in order to pay his respects and offers his condolences to Ukitake. On his way out, he happens to pass by a young Kotaro. While normally Yamamoto would be far too busy to waste time on an officer of such low rank, this is a solemn day. Thus, for once, he has empathy to spare and offers his condolences to the nebulously-low-numbered-seat as well. They have a conversation that spins off from there.
In a different world of steampunk wonder, Kotaro's skill with his air canons catches the eye of billionaire unintentional-playboy philanthropist Ukitake Jushiro. Ukitake takes such a liking to the street cleaner that he takes the young lad to Yamamoto. Unbeknownst to anyone outside his inner circle of Ukitake, Kyoraku, and Unohana, Yamamoto is the real power behind the city. He founded it, he owns 90% of the buildings and utilities within it, and the actions and agendas of his key agents make sure that everything keeps running in relative order. Kotaro, ever the humble street cleaner, has suddenly been thrust into a much bigger world with much darker alleys...
When Yamamoto was killed by Ywach, his soul was absorbed by the Emperor even as his corpse was messily desecrated. However, the process of converting Ywach into the new Soul King was as invasive as it was mind-bendingly cruel, and the unique methods involved caused Yamamoto's soul to be flung free from Ywach's grasp. Reborn in a world he does not recognize, with only a tattered uniform and Ryujin Jakka to comfort him, he is left unsure of what to do with himself and his new lease on life. As he learns about this new world and its strange ways, he eventually ends up forming a guild of his own called Koryu Dawn. Thanks to both the new Guild Master's natural strength and his talent for finding worthwhile individuals, Koryu Dawn experiences a fairly quick rise in notoriety. However, Yamamoto's new life hits a new snag when a joint mission with Phoenix Grave causes him to encounter a fellow refugee of his old world...