Some lore context on why is Suigetsu carrying Karin's dead body under the cut (:
I've been thinking about Karin in TToMUH. She's not exactly portrayed as a happy human, still working at Orochimaru's in her old age, having terrible relationship wirh her dauther, not willing to do anything for Menma and his friends (for the record - they asked her a thing that was very important to saving Konoha and also was capable of). Suigetsu is a rather nice man in this AU, he doesn't really has any problems. Orochimaru couldn't even do anything bad to him after 4th war because Kirigakure literally said "if you touch The Child we'll break ur stupid village" and he has to obey.
But Karin? Oh, that's certainly where he had his plans. Uzushiogakure couldn't exactly say the same as Kirigakure, leaving Karin helpless in his hands. First, she has returned from the war, believing that Orochimaru has changed... only for him to slap a Cursed Seal a few years later on her and say, "it you won't obey I'll kill you. I'll kill Suigetsu. I'll kill anyone you love", forcing her to continue doing horrible stuff. I think that even Shingetsu's birth was, in fact, requested by Orochimaru, who wanted to have a specimen of Hozuki hiden and Uzumaki jutsu mixed together naturally. (Through, Kirigakure found out about that too quickly and also said "u can't touch that child either"). I think that her seal won't even allow her to speak of it, just like Konoha's Root ANBU Seal.
And she grew tired. She started writing a diary where she wrote all of stuff that happened. How she was put a seal on, how she wanted to go home, how she didn't want to do all that stuff, how Orochimaru threatened her family, how stupidly she feels because of having to deal with her daughter. How afraid she is. How she's sorry for everyone.
One day, Suigetsu and Shingetsu decided they are tired of Karin and they should moved on to Kiri. Shingetsu left first with Menma's team, while Suigetsu stayed a bit longer, collecting their stuff and things like that. They obviously didn't want Karin, whose behaviour was not very well to say at least, to follow them, which Suigetsu explained to her. Karin had a last request for him to bring her diary before she left and he did it, peeking into it out of curiousity.
He read it, and she left a message that she was sorry on the last page. That she knew she'd die once he opened the book - because the seal will kill her once anyone knows of it. And her last wish, to be buried in the place that was home for her ancestors — the Uzushio island. At that moment Suigetsu probably didn't care much about Karin, but he still carried the body and buried her in Shingetsu's presence... which become critical in Kiri's campaign against Orochimaru alongside with his own case.
Karin's body rests in peace... would be nice to say "protected by her ancestors' souls", but actually protected by very much living Uzumaki on the island, while Shingetsu and Suigetsu report to Mizukage about that.
















