TOKYO—Nintendo Co. on Monday turned to Tatsumi Kimishima, a former banker and veteran operations person at the videogame company, to fill the top post left vacant by the July death of longtime PresidentSatoru Iwata.

The choice of a number-cruncher as the leader of a company famous for characters such as Mario the plumber might have puzzled some fans who hoped Nintendo would tap an internal rising star or an outside creative talent for the post. Mr. Iwata had a background in game development and even after he became president,...