After graduating from Tokyo Zokei University, Ito joined Square in 1987. He initially worked on Final Fantasy and Final Fantasy II as a debugger but first became genuinely involved with game development while creating sound effects for Final Fantasy III. His next major role was as the designer of the Active Time Battle system for Final Fantasy IV. Square filed a Japanese patent application related to the ATB system on 16 July 1991 and a corresponding US application on 16 March 1992. One Japanese patent (JP2794230) and two US patents (US5390937 and US5649862) were granted based on these applications. For Final Fantasy V, Ito designed the fully customizable Job system. He also created the 'Chicken Knife or Brave Blade' choosing event. Final Fantasy VI marked the first time that Ito became a director on a game. For this title, he was in charge of all battle aspects. He was also responsible for the battle systems in Final Fantasy VIII and Final Fantasy Tactics before he once more took on the role of director with Final Fantasy IX. Ito had the idea to make its protagonist Zidane Tribal flirtatious towards women.
In mid-2005, Square Enix announced that Yasumi Matsuno had left the company due to an illness but would be acting as a supervisor on Final Fantasy XII. Ito was appointed as the director of the game. Matsuno apologized for the long development time of the project but guaranteed players that it was "progressing in its development under the hands of excellent staffs". Ito created the License Board of Final Fantasy XII with the intention to give the player much freedom in developing characters to their liking without becoming too complicated. At the Square Enix Party 2007 pre-conference meeting in May 2007, he was introduced on stage as the producer and director of the newly announced Final Fantasy XII International Zodiac Job System. He stated later that he considered the game design and battle system of Final Fantasy XII a "definitive contribution to the gaming lexicon" and that it had "the potential to shine in future games". In about 2012, Ito was tasked by producer Shinichi Tatsuke with the creation of a battle system for a new game. However, the plan changed and he was told a week later that there was a different project to consider. Tatsuke now requested a concept for a social game which he felt was an interesting opportunity to have Ito work on, given his experience with simple Nintendo Entertainment System game systems. This concept became Guardian Cross. In September 2012, Ito said that he would work on another Final Fantasy game if the company's president wished for it. The corporate executive of Square Enix's 1st Production Department, Shinji Hashimoto, mentioned in July 2013 that Ito was "planning and doing some proposals for a new project" and "putting some ideas together".