Inui was born in Omihachiman on June 2, 1988. After graduating from Yasu High School, he joined J1 League club Yokohama F. Marinos in 2007. However he could not play many matches and he moved to J2 League club Cerezo Osaka in June 2008. Cerezo was promoted to J1 end of the 2009 season. He played 114 matches and scored 35 goals for the club. In summer 2011, he moved to German 2. Bundesliga club Bochum and played in 1 season. In 2012, he moved to Bundesliga club Eintracht Frankfurt. He played 75 matches and score 7 goals. In summer 2015, he moved to Spanish La Liga club Eibar. He played 89 matches and scored 11 goals in 3 seasons. In the 2018/19 season, he played for Real Betis and Deportivo Alavés. He returned to Eibar in 2019.