Last month, the Championship outfit were linked with a surprise move for Ideguchi, who has represented Japan on 11 occasions.
The Yorkshire giants have now decided to push through with a transfer, and Ideguchi is focused on making an impact in English football.
The 21-year-old told reporters: "I felt like I needed a new challenge, to help me develop further as a player.
"Hopefully I can deliver some good news to people back in Japan rather than have people wonder where I disappeared to."
Leeds have said that Ideguchi is likely to join Spanish side Cultural Leonesa on loan until he qualifies for a British work permit.