Yuuyake Koyake ist, soweit ich das mitbekommen habe, eine Art Mouseguard in denen die Spieler Youkai-Kinder spielen. Der Comic dazu ist recht lolig, aber leider nicht übersetzt.
That's a neat idea, but it's not a part of YK as written. The setting strongly emphasizes the idea that henge are animals who happen to be able to take on human form, and even if two scenes come immediately after each other, you still have to pay the transformation cost to maintain it. For that matter, apart from accumulating Memories and Threads (more on those later), there isn't any character growth per se. That's partly because the game is focused more on small-scale, short-term play. It specifically says that it's meant for 2 to 4 players, and (for example) the マレビト/Visitor character type in the Mononoke Koyake sourcebook has an optional Weakness that basically forces the character to permanently leave play after one story.
In addition to the henge, the people of the town, and ordinary animals, there are 土地神様, or "Local Gods." These are beings who protect a particular small area, and don't really concern themselves much with anything outside that area. They often take the form of things like insects, fish, or reptiles, though they can take human form if they want too.
Connections, Wonder, Feelings
In terms of its overall sensibility, I would describe Yuuyake Koyake as being like a hybrid of Japanese and indie sensibilities. (Though the designer has only had contact with indie stuffs through the バカバカTRPGをかたる column in Role&Roll magazine). It has relatively few rules, all focused towards a specific kind of play, and it alters or outright discards conventions of RPGs where it serves the game to do so.
The heart of the game is in the flow of Connections to Wonder and Feelings. You set up Connections to the town and to each of the other PCs before you start a story. A connection has a Strength (a number from 1 to 5) and Contents (what kind of bond it is; Admiration, Affection, Rivalry, etc.), and connections go two ways. One character's connection towards another has a Strength and Contents separate from the partner's connection back at them.
At the start of each scene you gain points of Wonder equal to your connections towards others, and points of Feelings equal to your points of connections from others. (Contents are pretty much purely descriptive). You can spend Wonder to use your henge's special powers, Feelings to boost your attributes for action checks, and transforming uses a mixture of Wonder and/or Feelings. Players can also award Dreams to other players (and the Narrator/GM) whenever a character do something neat. Between scenes you can spend Dreams to strengthen your Connections. However, when you first meet someone you can make an "Impression Check" on whatever attribute you want to use, and create a new Connection with a strength of 1 or 2.
At the end of the story, you lose all of your current Connections, but you get Memories points equal to your total non-town connections to others, and a Thread for each Connection you had. Memories can be used as Wonder or Feelings, but they're gone once you use them. Threads record a person and the contents of the former bond, and if they show up again in a subsequent story your new Connection to them has its strength increased by one (and you can accumulate multiple Threads towards the same character).
If you look at the character sheet, you'll notice that the little arrows neatly illustrate the general flow of stuff. Also, all this makes scene framing very important to how the whole thing works, and if the replays and scenarios in the book are any indication, it's meant for the scenes to be relatively short, and tightly controlled by the Narrator.
Powers
When you create a henge, you also pick what kind of animal he or she is (Fox, Raccoon Dog, Cat, Dog, Rabbit, Bird). This gives you six pre-determined powers, and six pairings of an Additional Power and a Weakness of which you pick one to three. This is where it shows more of its Japanese TRPG-ness. Henge powers sometimes affect how Connections are formed, sometimes affect action checks, and sometimes let a henge do something a normal person can't. For example, Foxes get a こあくま power where their strange allure makes their connections stronger by 1, and lets them pick the contents of the other person's connection towards them. They also have an optional power called ふわふわ that lets them fly at a slow pace.
Supplements
Yuuyake Koyake has one sourcebook so far, Mononoke Koyake. It adds five new character types, all "mononoke" that rather than being animals with some mysterious powers, are creatures of pure mystery. The types are Michinoke (monsters that pester people on roads), Oni, Kappa, Ghosts, and Visitors. One neat thing about these is that they allow for variations. A "Kappa" can be a traditional Kappa, or just about any critter that lives in the water, including mermaids and what amount to fish henge. The Visitors are the most varied of all; the signature character is an alien, but they can as easily be witches, time travelers, or Santa Claus. The book has a short comic about a boy befriending a Michinoke, some more stories/dialogues about them, and two scenarios.
The most recent issue of A Local Paper (Sunset Games' zine thingy) has a preview and sample story from the game, and the designer's doujin circle has included some Yuuyake Koyake stories in their anthologies, and even put out a 2008 YK calendar. At Comiket 73 they apparently were giving out rules for mouse henge, but the website says these will be revised and re-released later. The Sunset Games blog also obliquely mentions that Kamiya-sensei is thinking about another supplement.
The guideline in the book is for characters to be between 8 and 18 years old in their human forms, (though their chronological/animal ages can be anywhere from less than a year to a few centuries, depending). Although it might make for an interesting hack to the game, as written Yuuyake Koyake has no endgame at all, and it specifically emphasizes how henge are first and foremost animals, are defined by and happy as such, and have to exert themselves somewhat to maintain a human form.
One of the books on Japanese myths I was reading says that "folk legends" are a kind of folklore that consist of stories that don't necessarily need a narrative structure, and are fixed in a particular local place. It occurs to me that Yuuyake Koyake is in a sense a game about folk legends, albeit ones with a deliberately heartwarming tone.
Another thing is that in his book "Shared Fantasy," Gary Alan Fine says gamers tend to create what he calls "folk beliefs." In, say, D&D these tend to be along the lines of "Heroes will triumph over evil in the end," but for YK they're more reinforced by the game's text, and they tend to be more like "There's always a way to make someone happy."
If the included replay and two scenarios are any indication, YK is meant to be fairly tightly controlled by the Narrator. In all three cases, the game is basically set up with 4-5 scenes that establish and resolve a situation (e.g., a kid goes back to school to get something he forgot, but hears scary sounds from within, the henge persuade him to go in anyway, and it turns out to be a puppy that they have to figure out what to do with), and then there's an "epilogue" scene where the henge essentially get to see the fruits of their efforts and spend a little more time with whatever new friends they've made (if the boy adopted the puppy, they come visit the boy and his new pet and play for a while). So, basically, the Narrator says, "The next scene will be the last one," and after that one, the story comes to a close. Although there's no reason you couldn't do something like your example of trying to resolve a family's problems, the examples have thus far been on an even smaller scale than that.
Reading through the Visitor description did get me a little misty-eyed, to be honest, and I immediately decided I want to run a scenario where henge have to help a quirky time traveler (or some such) get home. I'll have to see how the game's default style works for me in practice, but what I would do is set up the scenario to be about how the henge help the visitor find her missing MacGuffin, and then the final scene would be the tearful goodbye. Of course, I should mention that Mononoke Koyake specifically says that mononoke are more difficult to play, and you should get some experience with playing henge first. Aside from the fact that, unlike henge, their natural forms usually scare people, mononoke also can have complications like the "Traveler" weakness (where they have to leave at the end of the session) that can make it more challenging to work out how the session should flow.
YK can definitely be played for multiple sessions--the rules for Memories and Threads only actually matter if you do--but it seems like it'd work best as a thing where you'd play every now and then, and swap out characters freely. That said, playing more in the long term, and thereby getting to know the town and the people (and other things) that live there could be a lot of fun too.
Oh, another thing I noticed while re-reading the rulebook some today: Although there aren't any rules for it, it often mentions about how some animals (and in Mononoke Koyake, mononoke as well) can potentially become local gods.