He's happy to join in. 

He's slowly coming to terms with the idea that maybe he deserves these snatches of happiness.

Despite having learned much of Kiritsugu over the last half-year, everything he's been willing to share, this odd family has accepted him, and seem unimpeded in their own happiness by his presence. If they wish to share that happiness with him, who is he to refuse their generosity?

After an enjoyable morning, Thia has warmed up a few cups of broth to fight off the chill of the wintry outdoors, and the four of them begin putting together a big holiday dinner,

He helps out where he can, and can't help but be swept up in the festivities.

They’re pretty efficient with the cooking, but it’s a big meal to make so he can still help fetch ingredients or watch the pot or things like that.

It takes a couple hours, which ensures everyone’s got a good appetite for dinner. There’s a little bit of everything they have to eat, including plenty of festive spices from the green room, and the the meat of one of the chickens, who had grown old and suffering over the last couple days.

He participates in the festivities as much as he can, but he's also thinking about what he could wish for. What he wants.

"Is it able to give information?" he asks. 

It certainly can. Thia, Bran, and Ira can all provide examples of when they’ve wished for the answer to a question, or to simply know more about a topic, and even without asking the Hearth adds instructions on how to care for new plants they wish for to the almanac.

Fascinating. 

Has it answered questions about itself before?

Sometimes! Anything...ordinary? The exact criteria is a bit hard to pin down. Specific questions about what it can do, for example, seem to be reliably answered, but questions like 'Where did the Hearth come from?' or 'How does the Hearth grant wishes?' are either answered cryptically or not at all.

Could he ask about the cave beast? 

He's curious about it. 

It can, though like with questions about itself, sometimes it's unable to give an understandable answer. They've already asked it about how to get rid of the cave-sleeper many times, in many different particular phrasings, and it hasn't been able to offer an options they can actually use.

What if it's more a general question about what it is? 

That would probably work! But they already mostly know what it is? It's some kind of bear or something bear-like that had control of the Hearth before Thia first came here and seemingly absorbed some of its power.

Oh, interesting. 

How did Thia manage to wrest control of the Hearth anyway? That's an impressive feat of magic if he's ever heard of one. 

She doesn't know exactly why, it's never been important enough to ask, but her strong suspicion is that the cave-sleeper hadn't needed to defend its control of the Hearth for a long time, if ever, before she arrived. She was lucky, and its guard was down. She stole it, followed her intuition as to how to hold and move the flame. She believes that it guided her, all the way here on the opposite side of the pines.

He still can't think of a wish, and decides he should probably stick to helping out with the festivities for the night. 

The eve of Wishing Night is no time for work! All the tasks for today were done before lunch. Instead, the afternoon and evening are filled with storytelling around the Hearth. Thia takes the lead initially, but Ira provides the most stories overall, drawing from her seemingly bottomless well of imagined worlds. The family will encourage Kiritsugu to contribute at least one story of his own, though they won’t push.

It takes him a long time to think. When he finally speaks, it's as though he's not fully the one telling the story. 

"There are other worlds," he begins. "Ones which seem familiar but are truly alien. From one of these worlds came a strange tree, bearing strange fruit. It had no name--not yet--nor did it have the will to do anything but answer the will of a planet that wished to die. This strange tree, which bore the shape of a fish, of a sea-faring vessel, of great wings scattered over with angels, died a death it did not understand, but its nature would not allow it to die. It is with that death that it began to understand love, and hope, and the desire for the world to keep on going. This is a story of the future, and the past. Love, death. We walk alongside both easily."

There had been dreamers at the Clocktower who imagined the end.

Bran listens with patient interest, and Ira with enraptured fascination already only barely holding back a deluge of new questions, but Thia herself seems to be struck by this introduction in a deeper way, her eyes suddenly full of dark memory and razor-keen attention.

He answers Ira's questions the best he can, admitting quickly that this is a world he has not seen, only heard of, but he notices Thia looking at him. 

"Do you remember this world?" he asks.

Ira, as she is wont to do, quickly turns from questions to speculation and postulation when answers become scarce. It may be a bit strange to see her imagining a world quickly diverging from what Kiritsugu himself pictures, or it might not.

"No," Thia answers quickly. "But the idea of the world dying, and of strange things descending upon its death, does call to mind the devastation I was originally fleeing when I found the Pines. Skies stained night-black and blood-red by the smoke and the dust..." She signs, and strokes a hand through her silver hair. "I'm sorry. I may share another story of my own after you but I didn't mean to interrupt. And, Ira, please control yourself, Kiritsugu is in no danger of suddenly forgetting this story I'm sure, you can press him for details tomorrow."

Ira blushes and casts her eyes down in chastisement. "Yes grandmother."

He can't help but smile at her eagerness. 

"I understand. I don't have much else to say, other than I think it shows that humanity persists for a long time, and that love is much stronger than I sometimes wish to give it credit for."

Ira smiles back to him. He will definitely be roped into more worldbuilding discussion later.

As she said, Thia will give the next story, though it turns out to be as much her attempt to recall as much about her old world as she as it is the story of its ending and her escape to the Pines. It goes on for a while, but towards the end, as Thia is actually describing the events of the end, as well as her mindset as she experienced it, Kiritsugu may be able to draw some parallels with what he himself experienced in the burning of Shinto.

It's dark outside by the time she finishes, and it seems the time for storytelling has come to a close, Bran begins cooking a small supper, just some hearty broth to give everyone a bit more life for the remainder of the evening, after which it will be time for the ritual of Wishing Night itself.

He realizes want he wants now. 

It feels silly, so he needs to ask first, but...

"Can it make icons of people it doesn't know?" 

He's never going to see his loved ones again, but...

He thinks of the angel, and of Irisviel. 

He wants to at least sort of see her again. 

Thia nods. "As long as you know, or there is some other way it could identify the right person, yes. Now, the time comes for us to begin."

With that said, the old woman gathers the four of them together close to the hearth before kneeling down right up close to the grate. "Oh dear hearth, old flame, our warmth and our friend, we are gathered here to give you our gifts and give you our wishes. It has been a year since you last awoke, and it is time to wake again." She intones reverently.

There's an immediate reaction from the fire, growing taller and its warmth spreading further through the room. Kiritsugu can also sense the magical potency of the hearth begin to spike. A tongue of flame reaches out from the hearth, stretching between the bars of the grate before waving once over Thia's kneeling form then retracting back into the fireplace. There's a palpable sense of recognition, acknowledgement, acceptance, and countless subtler emotions that permeates the action.

"Bran, Kiritsugu, please bring down the gifts." Thia requests.

He does so, overtaken by a surprising degree of reverence. 

He hasn't thought of Iris in ages.