Ken will be periodically checking on at the med car like Wen Qing told him to just for keeping track of his weight. He's underweight by a good few pounds before he reaches 'slight', so that needs to be kept track of.

Otoha will inevitably get hurt on mission so Ichigo may need to yell at him for that.

Casper will check in the med car (we've already talked about that) and will be happy to explain his weird biology as much as he can. He'll also explain his first aid healing skills (don't ask him to do anything with putting hands into bodies, he'll just stare into the distance remembering the Cerberus Incident) and general willingness to be a listening ear if someone needs it. He can also give Ichigo dreamless sleep if he wants, or work on making Ichigo something to absorb bad dreams.

And also I think they probably have a good bit in common? Kids who could see ghosts their whole lives, suddenly find out their parentage is not as normal as they thought it was, chucked into a world of fighting they did not understand...