Up AU! Saruhiko is a cranky old man who has recently lost his love Misaki. They meet each other just like in canon, fell in love and share their lifes with ups and downs till' the end. Saruhiko is devastated, but then one day, this brat Munakata (boy scout of course) came speaking of the airship he chased with Misaki when they were young and together end in an adventure with an evil green king interested in an isolated king, and all the characters involved with those individuals + Sarumi feeling
Tiny boy scout Munakata and cranky old man Fushimi would be a lovely combination. So maybe Fushimi’s early life was similar to canon, he had shitty parents and grew up mostly alone. He sometimes likes to run off to this empty house next door and hide in the attic reading or playing on his computer, he’s doing that one day when this short energetic redhead appears having come looking for treasure. The kid introduces himself as Yata and tries to get Fushimi to play with him, Fushimi refuses and makes a run for it, which is when he falls through a bad spot in the floor and ends up breaking his leg. He’s miserable and stuck alone in his house when Yata sneaks in the window, having been super worried about him. Yata’s so confused as to why someone injured like Fushimi would be all alone, like why aren’t his parents taking care of him, and Fushimi just clicks his tongue and looks away. Yata decides to take care of Fushimi himself and thus wins Fushimi’s undying affection. The two of them stay together as they get older, they get married and Fushimi is totally devoted to Yata. The two of them even plan on one day going to visit this rainforest paradise they’ve seen pictures of in books, one day when they were young they chased an airship that was supposed to belong to the great explorer Adolf Weismann who went missing in the rainforest and they think it would be cool to go find him. They’re never quite able to get there though, life always getting in the way, and finally Yata eventually gets ill and dies, leaving cranky grumpy Fushimi all alone and devastated.
After that Fushimi isolates himself in his house, refusing to leave for any reason, even when all the houses around his are sold to a developer. The developer keeps trying to get Fushimi’s house too, one day one of the construction guys even comes into Fushimi’s yard and breaks Yata’s old skateboard that was propped against the door, Fushimi gets pissed and throws a knife at the guy. Because of that the developer’s able to get a court order that Fushimi has to leave, Fushimi’s like fuck that and starts making plans to escape. He uses a bunch of balloons to make his house fly, figuring he’ll go to the rainforest by himself not even to find adventure but just to get some fucking peace and quiet. That’s when there’s a knock on the door and Fushimi finds himself staring at a stowaway, a small respectable looking boy scout with wire frame glasses who has some suggestions on how Fushimi could possibly increase his navigational abilities, if Fushimi would just allow him to come inside. (I can see this happening like in the movie too, just imagine Fushimi being all ‘no’ and slamming the door. Then he sighs and opens it again all ‘come in’ because Fushimi is weak to small children).
Fushimi and Munakata eventually land in the rainforest, Munakata is very impressed with all the local wildlife and wishes to take pictures for future observational study, Fushimi wonders if this kid is ten or fifty. On the other hand this way Fushimi can make the kid help drag the house forward so Fushimi doesn’t have to do it. While they’re exploring Munakata finds an adorable pink kitten and starts playing with her, Fushimi wants to get rid of the kitten because his allergies are acting up. That’s when they’re both met by a friendly talking dog named Hidaka who works for a man known as the Green King, he’s searching for a mythical pink cat. Fushimi can see drama coming and tries to lose the stupid dog, but he and Munakata are soon caught by Yukari, the world’s most fabulous dog, and taken to see Hisui. Hisui’s an adventurer who also came here in his own airship searching for the lost explorer Weismann, who it’s said is living somewhere deep in the forest with a rare pink cat. Fushimi’s like 'here’s the cat, can I go now’ but Hisui has already decided that Fushimi wants to steal Weismann away from him and tries to have the dogs chase him down. Fushimi sighs, throws a few knives, and tosses Munakata and Neko over his back as he outruns the dogs and escapes, Hidaka manages to follow along with them and joins up.
Once they get to safety Fushimi’s pissed that he had to do any of this to begin with, he storms into his house and tells everyone to just leave him alone. While he’s sulking in his house though he finds this secret scrapbook that Yata had hidden which got dislodged with the house being tossed around. In it are all these pictures of Yata and Fushimi together, smiling and being happy and there’s a note at the end telling Fushimi not to be afraid to make more precious things and that he’s worthy of having other people care about him. Fushimi decides fine, fine I’ll help get the cat back to Weismann, which is when he steps out of his house to find Neko and Munakata have been kidnapped by Hisui. With Hidaka’s help Fushimi storms Hisui’s airship, gets the dogs out of the way (he lures old dog Iwafune away with a trap using a beer can as bait and does the same with Yukari and a tube of lipstick, while Munakata ends up lecturing tiny yappy puppy Sukuna to sleep). Hisui is defeated and Fushimi takes control of his airship, taking it to the middle of the rainforest where Weismann is totally living the jungle life with a bunch of rare pink cats and a single black dog, Fushimi decides he doesn’t want to know and is just like here’s your cat, I’m going home to a place where there’s air conditioning. Munakata’s very attached to Fushimi by now though and has decided that he will be Fushimi’s unofficial grandson, asking if perhaps he would like to go for ice cream once they get back to civilization.