“I love red wine, it’s my favorite thing!” These are perhaps not the words that a mother particularly likes to hear from her young daughter — especially when she is only 4 years old.

But this was precisely what my daughter told me when we recently paid a visit to one of Japan’s less conventional attractions: an onsen (hot spring ) theme park called Yunessun Spa Resort.

Located in the mountains of Hakone, Kanagawa Prefecture, Yunessun is hot-spring nirvana — with a quirky twist. Not only is it home to an expansive Japanese-style hot-bath experience, it also has an array of unique offerings, in particular, a series of baths made with ingredients such as coffee, green tea, Japanese sake and, my daughter’s favorite, red wine.

It was on a recent mother-daughter trip to Hakone that our visit to Yunessun took place. We were staying next door at the complex’s shiny new sister hotel the Hakone Kowakien Tenyu, which opened in April.

The newly built hotel taps into the modern ryokan (Japanese-style inn) theme, with a mix of contemporary clean-lined design, walls of glass framing green mountain views, and 150 tatami mat rooms with private ceramic hot-spring baths on each balcony.

It is here that our onsen workout warm-up took place. As soon as we arrived, we slipped into our cotton yukata robes (there’s a selection of children’s sizes, including slippers), and we made a beeline for the hotel’s communal onsen baths.

Here, my daughter indulged in her favorite bathing activity of filling up the wooden bowl at the tap with an overflowing mountain of soap bubbles before we rinsed off and enjoyed a soak in the hotel’s serene baths, both indoors and out.

Dinner followed, with a very child-friendly kids menu alongside the adult’s kaiseki-style (multi-course) banquet, before one of the highlights of our hotel stay took place: an evening soak in our private balcony bath, beneath the stars.

For my daughter, however, the best was yet to come: Following an early morning yoga session in the hotel gardens, with nearby waterfalls providing a serene mountain soundtrack, we checked out and headed a few minutes down the hill to Yunessun Spa Resort.

The change of aesthetics and slightly tired decor didn’t bother my daughter at all. She raced into the changing rooms, slipped into her swimsuit and — clearly seduced by pictures of red water she had seen earlier on the Yunessun website — jumped up and down as she demanded: “Red wine bath! Red-wine bath!”

A little perturbed at her early embrace of red wine, I led the way into the main onsen area, filled mainly with families as well as groups of schoolgirls and young couples.

We skipped the large indoor swimming pool-style onsen in the heart of the complex and instead found the red wine bath hidden in a cave-like space, complete with an oversized bottle pouring a steady stream of “red wine” onsen water into a warm red pool.

My daughter immediately made her way to the bottle and began opening her mouth, resulting in my first, but not the last, exclamation of “don’t drink it!”

The next two hours passed in an onsen frenzy. We soaked in a teacup-shaped black tea bath, a green tea bath and a sake bath. We also played in the onsen jacuzzi-like swimming pool — both indoors, dramatically named The Gods’ Aegean Sea, and outside, although we left the big water slides to the older children and were too squeamish to visit the feet-nibbling doctor fish pool.

We stopped for a fairly basic fast-food-style poolside lunch of spaghetti carbonara before my daughter dragged me to the Coffee Show, which involved us standing expectantly in murky warm brown water before a member of staff nonchalantly tipped a bucket of coffee over our surprised heads — as sticky and aromatic an experience as you might imagine.

Despite all the different baths, we returned again and again and again, to one place: the red wine bath. It was only when it thankfully changed to white wine — nowhere near as much fun apparently — that my daughter permitted me to even raise the controversial idea of perhaps going somewhere else.

We finished our onsen-fest on the more serene Japanese-style floor of Yunessun — Mori no Yu, a network of swimsuit-free and red wine-free bathing, both indoors and outside.

On the train back to Tokyo, we counted how many baths we had indulged in over the previous 24 hours and came up with an impressive 16. And the best? Well there was one clear winner, of course, at least in my daughter’s eyes: the red wine bath.

Hakone Kowakien Tenyu (www.hakone-tenyu.com) has doubles from ¥35,790, and guests receive discounted tickets to Yunessun Spa Resort (www.yunessun.com), with adults costing from ¥2,800, children ¥1,500. Full-price tickets to the spa resort are ¥4,100 for adults and ¥2,100 for children.

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