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 iPhone and 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.

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.

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 given more free content if they were to pursue a free-to-download model",  he said.

Source: WSJ