His first three years on his youth football career was unusually played in three different clubs. He played on Chuo FC, Street FC and Aburayama Camellia between 2006 and 2008. He joined theGamba Osaka academy in 2009. He made his first team debut with Gamba Osaka in 2014, he joinedJ.League U22's on loan in 2014 to get first team experience.[citation needed]
During the 2016 JLeague season Ideguchi was named 'New Hero Award' and the prestigious 'Rookie of the Year' award for the JLeague. After almost ten years spent withGamba Osaka between youth ranks and senior team he left the club after 60 appearances in the JLeague scoring 8 goals.[citation needed]
The same day after signing for Leeds, he went on a half a season loan to Leeds's feeder team in Spain,Aspire Academy owned clubCultural Leonesa with the club wanting to ready Ideguchi for European style football.[4] On 28 January 2018, Ideguchi made his debut forCultural Leonesa againstCA Osasuna in a 2–1 defeat.[5]
After returning for the start of pre-season under new Leeds Head CoachMarcelo Bielsa,[6] Ideguchi made his first appearance in a Leeds shirt when he started for Leeds in the pre-season friendly 1–1 draw againstYork City on 20 July 2018.[7] Despite starting for Leeds in three of their pre-season friendlies, on 26 July 2018, Ideguchi was seemingly not given a shirt number for Leeds for the upcoming2018–19 season for Leeds.[8] However, the following day 27 July, he was listed with shirt number 16 shirt in the club's online store.[9] By early August, Bielsa praised Ideguchi's professionalism and hard work since his joining Leeds United, but admitted he did not see him as first or second choice for any position, and indicated he did not think it would be fair to ask him to stay at the club.[10]
On 21 August 2018, Ideguchi joined2. Bundesliga sideGreuther Fürth on a season-long loan deal with an option to make the deal permanent.[11] On 15 September, he scored on his Greuther Fürth debut in the 4–1 win againstHolstein Kiel.[12] On 30 September, he was substituted in a 1–0 win overDynamo Dresden with what later was revealed to be aposterior cruciate ligament injury, expected to keep him out for most of the season.[13]
Having spent the initial part of his rehabilitation in Japan, Ideguchi returned to Germany at the start of 2019. On 6 May 2019, he made his first competitive appearance after the injury, coming on as a substitute as Greuther Fürth lost 4–0 at home to1. FC Köln.[14]
On 31 December 2021, Ideguchi was announced to have signed forScottish Premiership clubCeltic for an undisclosed fee.[17]
On 17 January 2022, Ideguchi made his debut for the club in a 2–0 win againstHibernian in the Scottish Premiership.[18] A few days later, Ideguchi would start in aScottish Cup fourth round tie againstScottish League One sideAlloa Athletic. While Celtic won 2–1 and progressed to the next round, he sustained a serious injury and was forced off late in the game due to a strong challenge fromMouhamed Niang.[19][20]
Ideguchi got his first call up to the seniorJapan squad for matches againstOman andSaudi Arabia in November 2016.[23] On 31 August 2017, he scored the second goal when Japan beat Australia 2–0 and qualified for the 2018 World Cup in the process.[24][25] On 9 December 2017, Ideguchi scored the winner for Japan in a 1–0 victory againstNorth Korea in the2017 EAFF E-1 Football Championship.[citation needed]
On 15 March 2018,Vahid Halilhodzic surprisingly left out Ideguchi andTakuma Asano for theJapan squad for friendly matches withMali andUkraine in preparation for the2018 FIFA World Cup, with Halilhodzic describing Ideguchi's lack of regular game time atCultural Leonesa he proclaimed 'It makes me sad that Asano and Ideguchi are not playing, They were the heroes of our qualifying game againstAustralia. They haven't been chosen this time, and if things continue the way they are, there is a chance that they won't be chosen for the World Cup."[26]
On 17 May 2018, Ideguchi was named in new Japan Manager'sAkira Nishino's preliminary 35 man squad forJapan for the2018 FIFA World Cup in Russia.[27] Japan's squad was cut from 35 to 26, Ideguchi was named in the 26, and played for Japan on 31 May in a 2–0 defeat toGhana in a pre-2018 FIFA World Cup friendly, the following day, the squad was cut from 26 to the final 23 man squad with Ideguchi missing out.[28]