Japanese frogs are proliferating across Asia. The good news is, they’re not an invasive species, nor are they real.

Tabi Kaeru, or Travel Frog, became the No. 1 downloaded smartphone app in China for almost two weeks after its debut, and is still hovering at the top of the charts in China, Hong Kong, Taiwan, Singapore, Malaysia and Japan. The idea for the game came from Mayuko Uemura, a 26-year-old employee of developer Hit-Point Inc. who has never written a line of computer code.

The game’s objective is simple: pack a lunch, maybe a tent, plus a few other trip-friendly trinkets for your virtual amphibian and wait for him to come back from his travels with pictures and gifts. If the premise of gathering food and knickknacks while waiting for animals to show up sounds familiar, that’s because it is: Nagoya-based Hit-Point is behind the cat-collecting game Neko Atsume and came up with the latest hit. Both titles share DNA with Tamagotchi, Bandai Namco Holdings Inc.’s handheld virtual pet toy that became a global fad in the 90s and early 2000s.

Uemura said she was inspired by her passion for travel and the feeling of waiting for a loved one to return from a trip. 

“We are definitely making people wait, and sometimes I worry because I think: aren’t we making people wait too long?” she said in an interview. “I want to develop games that players can love. I don’t want to develop games where you have to focus too much.

Indeed, by no means is the game fast-paced. When the frog is inside his cave-like home, he’s usually scribbling or reading a book. It’s oddly soothing. By collecting clover in the front yard, you can use it to buy food, lanterns and anything else that might help on a long trek. After wandering about for hours or even days, the frog returns with souvenirs and snapshots from his travels. That’s it. The goal is collect more stuff: for the frog to take on trips, as well as the stuff he brings back.

Even though the game is only available in Japanese, it’s been downloaded more than 30 million times following its November debut (with China making up 95 percent of that), outpacing even Nintendo Co.’s hit title Animal Crossing released around the same time, according to researcher Sensor Tower. By comparison, Neko Atsume has been downloaded 22 million times.

It’s especially popular among women, according to Daniel Ahmad, an analyst at Niko Partners. Women account for almost half of players in Tencent Holdings Ltd.’s $3 billion hit Honor of Kings. “It shows that there is a huge opportunity to target female gamers in China,” he said.

While frogs are considered a symbol of fortune and prosperity in China and parts of Asia, Hit-Point isn’t saying how much it’s made from Tabi Kaeru. While there are ads that bring in revenue, users can also purchase additional clover as currency. There’s plenty of potential; Neko Atsume’s popular feline characters are now featured in toys, books and even a movie.

“I like the attitude it carries: living a simple life, no sophistication at all,” said Chen Jiajia, an accountant at a logistics company. The 29-year-old says she checks in on her frog, named fantuan, or rice ball, a few times a day.

David OReilly, a game designer whose work appeared in the Spike Jonez film “Her,” said games are evolving beyond button-mashing and puzzle-solving. Tabi Kaeru is a good example of one that strives to calm instead of stimulate. “The internet, games, the screens we look at also need quiet areas,” said OReilly, whose titles Mountain and Everything embody that spirit. “What we think of now as games will change radically in the next 5 to 10 years as more creators enter the space.”

It still isn’t clear whether Tabi Kaeru will be a hit outside of Asia. It hasn’t generated much buzz in U.S. And while 2014’s Neko Atsume gained popularity in Japan, South Korea, the U.S. and the Netherlands, for now the traveling frog might be limited to crossing just one pond.