Arsenal During his trial at
Arsenal in the summer of 2010, Miyaichi impressed the Arsenal manager,
Arsène Wenger, signing a professional contract on 31 January 2011. Wenger said: "We’re delighted that Ryō Miyaichi has joined us. He trialed with us in the summer and has raw ability which has attracted many clubs around the world".
Loan to Feyenoord in 2011. Just after he signed for Arsenal, it was announced that he was set to join
Feyenoord on loan. On 5 February, in his first appearance for Feyenoord, he played the full 90 minutes against
Vitesse Arnhem in a 1–1 draw, and was named man of the match. Miyaichi then played against
Heracles Almelo where he scored the opening goal and created the second in a 2–1 league win for Feyenoord. On 17 April 2011, Miyaichi scored two goals and contributed two assists in Feyenoord's 6–1 victory over
Willem II, leading a revival after Feyenoord had conceded an early goal. The Dutch media gave him the nickname "Ryodinho" after comparisons to
Ronaldinho. He has also been branded the Japanese
Messi.
2011–12 season As he returned to Arsenal after his loan spell at Feyenoord, Miyaichi joined up with the first team for pre-season training. He was included in the 23-man squad to tour Asia in the pre-season after impressing in training. Miyaichi made his pre-season debut against
Malaysia All-Stars XI, he started the match before being substituted for
Robin van Persie in the 66th minute. On 9 August 2011, Miyaichi was granted a work permit to play for Arsenal on the grounds of being an "exceptional talent" in view of evidence supplied by Wenger and the
Japan Football Association, and was deemed free to represent Arsenal during the 2011–12 season. He was also included in Arsenal's 23-man Champions League squad for the fixture against
Udinese. On 23 August 2011, Miyaichi featured in the
Arsenal Reserves against
Wigan Athletic Reserves and scored in the 83rd minute. On 20 September 2011, Miyaichi made his first team debut against
League Two side
Shrewsbury Town in the
League Cup third round as a 71st-minute substitute. He also came on again in the League Cup as a substitute as
Arsenal went on to win the match 2–1 against
Bolton Wanderers. During the reserve match against
Fulham, on 7 November 2011, Miyaichi lasted 34 minutes before being forced off with an ankle injury, which would cause him to be out for weeks. Despite being in the first team, Miyaichi admitted he still has a lot to learn.
Loan to Bolton Wanderers On 31 January 2012, Miyaichi joined
Bolton Wanderers on loan until the end of the season. Shortly after arriving at Bolton, manager
Owen Coyle spoke of his admiration for the young player, even though Miyaichi had yet to play in a competitive match for the team. He played a behind-closed-doors game on 7 February against
Preston North End where he scored the only goal in a 1–0 win and made his full debut when coming on as a half-time substitute for
Martin Petrov in Bolton's 2–1 home defeat by
Wigan Athletic on 11 February. He made his first start, and scored his first goal, the following weekend in Bolton's 2–0
FA Cup win at
Millwall. He played 78 minutes of the game before being substituted. He made his first Premier League start the following weekend in Bolton's 3–0 loss at
Chelsea. He was voted February Player of the Month by the Bolton fans after his debut.
Loan to Wigan Athletic match against
Wolverhampton on 7 October 2013. On 13 August 2012, Arsenal confirmed that Miyaichi had joined
Wigan Athletic on a season-long loan. On 28 August 2012, he made his debut as a substitute in a 4–1
League Cup victory over
Nottingham Forest. During his first game for the club he was able to provide an assist for
Callum McManaman. He went on to make his league debut on 1 September in a 2–2 draw with
Stoke City. On 9 March, he made his return as a substitute for Callum McManaman in a 3–0
FA Cup quarter final win away to
Everton. Miyaichi picked up injury during the game which saw him sidelined for the rest of the season. He thus missed the rest of Wigan's historic cup run where they went on to lift the
2013 FA Cup.
Return to Arsenal Miyachi made an early return to the Emirates from his loan move at Wigan due to injury. On 22 July 2013, Miyaichi scored his first goal for Arsenal in a friendly against
Nagoya Grampus during Arsenal's pre-season Asia tour, scoring a penalty-kick in the 26th minute. He went on to make his
UEFA Champions League debut on 28 August 2013 in a 2–0 win over
Fenerbahçe. During that season he made 10 appearances in the Eredivisie with the club's first team. Miyaichi also played 14
Jupiler League games with
Jong Twente, scoring three goals and delivering one assist. He returned to Arsenal at the end of the season when his five-year stay at the North London club was brought to an end. Miyaichi's transfer was confirmed on the club's website the next day, where it was revealed that he would wear the number 13 shirt for the upcoming season. One week before the
2015-16 league campaign began, Miyaichi tore a cruciate ligament in his left knee in the final warm-up game against
Rayo Vallecano, an injury that meant he did not make his competitive debut until nine months later in a home game against
Union Berlin in April 2016. On 15 May 2016, Miyaichi scored a brace in St. Pauli's 5-2 win over
FC Kaiserslautern. In preparations for the
2017-18 season, Miyaichi had another major set back, suffering from another cruciate ligament tear, this time to his right knee. On 27 May 2021, it was announced on the club website that Miyaichi would be leaving the club after six years. Miyaichi's time at FC St. Pauli was plagued by injury, he managed 80 appearances for the club over six seasons.
Yokohama F. Marinos On 5 July 2021, after having spent his entire senior career in Europe, Miyaichi returned to his native Japan, signing for
Yokohama F. Marinos in the
J1 League. Miyaichi was assigned the number 17 shirt and on 18 September 2021, he made his debut against Nagoya Grampus, coming on as a substitute in the 55th minute. Miyaichi only made one more appearance for Yokohama during the
2021 season, struggling with injury as they ended the season J1 League runners-up to
Kawasaki Frontale. On 16 April 2022, Miyaichi made his
AFC Champions League debut against
Vietnamese champions
HAGL, playing the full 90 minutes as Yokohama won 2-1. On 18 May 2022, Miyachi scored and assisted in an impressive performance against
Urawa Red Diamonds, the match ended as a 3-3 draw but marked Miyaichi's first goal and assist for the club. A week later, Miyaichi's form continued, assisting twice against
Kyoto Sanga before being substituted in the 74th minute. On 2 July 2022, Miyaichi scored a late goal against
Shimizu S-Pulse after coming on as a substitute, as Yokohama secured a 5-3 away victory. Four days later, Miyaichi made an impact off the bench again, scoring another late goal against
Sanfrecce Hiroshima in a match that ended 3-0 to Yokohama. Miyaichi's performances during the season saw him earn a re-call to the
Japan national team after almost a decade since his last international appearance in 2012. Miyaichi suffered another anterior cruciate ligament rupture in his right knee during Japan's final
EAFF E-1 Football Championship match against
South Korea and will miss out the rest of the season following surgery. Yokohama finished the
2022 J1 League season as champions, with Miyaichi selected as one of the players to lift the trophy. Miyaichi returned as a substitute in the
2023 J.League Cup Group A match against
Hokkaido Consadole Sapporo on 24 May 2023. On 10 June, Miyaichi scored his first league goal of the 2023 season against
Kashiwa Reysol in the 97th minute to win the match 4-3 after coming on as a substitute. == Style of play ==