Just a little headcannon for post series 9th division
When Kensei first proposed bringing back Mashiro as a fukutaichou the division was a little resistant, not wanting to lose Shuhei who had stood by them and pulled everything together for them in their darkest moment in the last century. However Kensei assured them he had no intention of letting Shuhei leave his post.
Shuhei and Mashiro divide up the work of the fukutaichou. Partially because Kensei feels Shuhei has done all of it for too long, and partially because Kensei actually needs them both around.
Shuhei is in charge of more paperwork and planning things. He sets up the guard shifts since the ninth division is still in charge of security. Shuhei also still runs the magazine department as well. He does the leave forms, the human resources, the requests for supplies, anything that requires detailed checks.
Mashiro is the one who does more of the training of the division as well as leading missions. It’s more because Kensei knows she won’t do any kind of paperwork then anything. Some of the division members are amazed by the fact she never uses her zanpakuto, but rather will kick or punch a hollow to death so quickly it never notices her presence.
Kensei takes on what he can from both of them while doing his own duties. He personally sees to both of their training, although it’s more Shuhei’s training then anything since Mashiro neither wants or really needs Kensei to train her anymore.
Cooking contests in the division are a thing, and every so often lunch for the whole division is just everyone judging some kind of cooking contest because two people got into an argument and that is one of the three ways they settle it in the ninth. The other two are a writing contest or a sparing match. However the first two were complimented because the first is good for the division moral and the second because Shuhei really needs more writers for the magazine.
Kensei acts rough and grouchy but he really does care about Shuhei and Mashiro a lot. The two have become two of the most important people in his life and he is not willing to let either of them go. However he has already set it up so when he does leave it will be Shuhei that will take over the division, which is just as well because Kensei knows if he retires Mashiro will just follow after him.
