"They say it's like having a child," she says.

"A child younger than 5 wants to be with their parents constantly. The frog is more like an adolescent. He's rarely home and doesn't like to talk with his parents. So, you can only pack luggage."

Travel Frog appeals to people who rarely play games, Sina Games' former chief editor Zhou Wei says.

Those who've played Neko Atsume: Kitty Collector will be interested in the company's new game, he says.

Travel Frog is currently only available in Japanese. So, some Chinese players have been voluntarily translating it into Chinese. They also share tips online, such as how to get photos of the frog with other animals, Zhou Wei says.

These translations and social-media interactions are crucial to the game's success, he believes. Some netizens download it after seeing such memes as cartoons and chat stickers with the frog as their motif.

"Most players are female … and they even call the frog 'son'. It's like raising a pet," he says.

"Unlike earlier popular mobile games, such as King of Glory (a multiplayer online battle game), Travel Frog doesn't require much time. It's a new experience for gamers. But the novelty may soon fade. The kitty's popularity only lasted about a month."

The Beijing News recently reported the rumor that Hit-Point Co Ltd developed the game to test whether people were willing to have children in the future.

Mayuko Uemura from the company told the newspaper the game targets females as young as 10 up to those in their 20s.

In the game, the frog leads a free and relaxing life－it often travels spontaneously－which is probably one of reasons for its popularity among the young people who are busy and stressed, according to Uemura.

"It's relaxing since it's not competitive," says Deng Xiquan, head of the Youth Research Institute of the China Youth and Children Research Center.

"Players feel empathy. Most are undergoing life transitions and can learn about parenthood. It may also remind them of their childhoods.

"You know the frog will return. But you don't know when. That creates a kind of happiness."