By Takashi Mochizuki

TOKYO -- Investors disappointed by early reviews and sales of the smartphone game "Super Mario Run" sold more Nintendo Co. shares Monday, with some analysts expressing concern over the game's payment model.

Nintendo shares finished down 7.1% in Tokyo Stock Exchange trading, extending a losing streak to five days, during which the stock has fallen more than 16%. The stock had risen more than 20% in the space of a month before beginning the slide.

"Super Mario Run," featuring the Kyoto-based company's most famous game character, was released last week for Apple Inc.'s iPhoneand other iOS devices. The app, unveiled by Nintendo game creator Shigeru Miyamoto at an Apple event in September, is free to download but requires $9.99 to unlock all the features.

Initial reviews on Apple's App Store were below par and sales missed expectations in some markets. The game didn't gain the No. 1 spot in Japan, one of the world's largest smartphone game markets, though it landed that position in the U.S. and elsewhere.

After a sharp run-up in Nintendo's stock price ahead of the game's release, analysts said the negative news prompted some investors to close out bullish bets.

Nintendo plunged into the smartphone game market this year after many years of avoiding it. The poor performance of the company's flagship console, Wii U, prompted investors to encourage the company to offer smartphone games featuring popular characters such as Mario the plumber.

Expectations for the Mario app were heightened by the summer craze for "Pokémon Go," a free-to-play smartphone game developed by a Nintendo affiliate.

But analysts pointed to differences between "Super Mario Run" and "Pokémon Go." The Pokémon game earns revenue from small in-app purchases by players, such as virtual incense to lure the animated creatures appearing on screen. Co-developer Niantic, a spinout from Google parent Alphabet Inc., has been adding fresh content to keep players' attention.

The Mario game, on the other hand, gives players only one chance to pay -- the $9.99 charge to advance to the game's higher levels. A Nintendo spokesman said the company didn't plan to release additional content, either free or paid.

"If you were hoping that Mario would perform like Pokémon, then Mario clearly didn't achieve its mission," said Hideki Yasuda, an analyst at Ace Research Institute. "But that was placing expectations too high because the Mario game's business scheme is so different from Pokémon."

Research company SuperData forecast that the Mario game would generate as much as $15 million in its first month, while "Pokémon Go" and other Pokémon merchandise helped Nintendo boost operating profit by about $100 million in the July-September quarter, when the game was released.

The Mario game isn't available yet on Alphabet's Android operating system, meaning at least one more big tide of revenue can be expected. But poor reviews on the Apple platform may hurt Mario's performance on Android, said Motoi Okamoto, a former Nintendo game director.

Mr. Okamoto, who said he has already finished the Mario smartphone game, said that it was well thought out but its payment structure wasn't ideal. Players who see that the game is free to download may get an unpleasant surprise when asked to pay $9.99 after just a few levels, he said.

"The game should have either asked players to pay when downloading or givenmore free content if they were to pursue a free-to-download model, " he said.

Write to Takashi Mochizuki at takashi.mochizuki@wsj.com

(END) Dow Jones Newswires

December 20, 2016 02:47 ET (07:47 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.