Nintendo's foray into smartphones is off to a good start.
Miitomo, a free messaging-based application, reached No. 1 among social-networking apps in Japan on Apple's iOS devices on the day of its release, market researcher App Annie said on Friday.
Line, the country's most popular instant messenger, fell to second place.
Nintendo is seeking to bring back players who migrated away from games on company's dedicated hardware, such as the Wii and handheld DS devices.
The Kyoto-based company has promised to bring hits like Super Mario Bros. and Donkey Kong to smartphones, helping to boost its share price 33 per cent last year.
So far, President Tatsumi Kimishima has been coy, saying only that Nintendo's next smartphone game will feature one of the company's beloved characters.
"This should remove any doubts about the Nintendo brand's relevancy in the smartphone age," said Atul Goyal, an analyst at Jefferies Group LLC. "More than just a messaging tool, Miitomo can be a platform for distributing Nintendo content, and probably third-party content at a later stage."
Miitomo, currently available only in Japan, lets users automatically generate a cartoon-like avatar using a photo taken on the smartphone. Players can tweak minute facial features, set personality parameters and choose the character's voice.
Then, Miitomo starts to ask questions that range from "what did you do last weekend?" to "what's your favorite kind of uniform?" Answers are rewarded with virtual coins, which can be used to buy clothes and accessories for the avatar.
Miitomo then encourages people to share their in-app selfies on Facebook, Twitter, Instagram and Line. The app also offers rewards for connecting with friends.
Nintendo plans to make Miitomo, a play on the words "me" and "friend" in Japanese, available in 15 more countries this month. The company has said it will roll out five games for mobile devices by March 2017.
"We had a good start and have received very positive feedback," Nintendo spokesman Yasuhiro Minagawa said, declining to disclose the number of downloads. "Miitomo will continue to evolve."