He was the first Japanese manager of the club for the first time in 21 years since Masakatsu Miyamoto in 1994 (except caretaker Takashi Sekizuka in 1998 and 1999).
In the final, after a 2–2 draw against European champions Real Madrid after 90 minutes, they were beaten 4–2 after extra time.
In November in late in 2017 season, Ishii signed with Omiya Ardija (former NTT Kanto) where he began his playing career.
[1] On 23 December 2019, Ishii was named the head coach of Thai League 1 club Samut Prakan City.
Ishii became the second Japanese head coach of Thailand, following Akira Nishino, who served for two years from July 2019.
Based on 4-4-2 formation, it is characterized by aggressive tactics that use high press and short counter to break through the center.
During his time at Omiya Ardija, he made good use of Genki Omae, who had a lack of scoring ability and was unsuccessful in the previous year, leading him to the league's top scorer.