Born in Fukuoka, Japan, Tomiyasu was first scouted by the Mitsuzuki Kickers’ general manager Kanji Tsuji, and was impressed with his performance, especially his speed. Following this, Tsuji invited his parents and convinced them to let him play football, which led Tomiyasu enrolled at Mitsuzuki Elementary School. When he was eleven, Tomiyasu was recommended for a trial at FC Barcelona Soccer Camp by his coach. He impressed at the trial that FC Barcelona offered him a place on the club’s youth academy but it was difficult for him to relocate to Spain and the move was cancelled. Despite this, Tomiyasu said the experience at the Soccer Camp gave him a put of good use.
After failing to join FC Barcelona, Tomiyasu joined Avispa Fukuoka. Initially playing in the midfield position, he switched to a centre-back position. During his time at Avispa Fukuoka’s youth system, Tomiyasu once served as a captain there. He impressed at the 2013’s JFA Premier Cup that he was named Best Eleven. In May 2015, it was announced that Avispa Fukuoka registered Tomiyasu. After appearing two matches as an unused substitute, he made his debut for the club on 14 October 2015 as a starter in a 2–0 loss against Machida Zelvia in the third round of the Emperor’s Cup. At the end of the 2015 season, Tomiyasu signed a temporary contract with Avispa Fukuoka.
At the start of the 2016 season, Tomiyasu spent the first half of the J. League season on the substitute bench. Tomiyasu he made his first appearance of the season on 20 April 2016, as a starter in the defensive midfield position, in a 0–0 draw against Vegalta Sendai in the J. League Cup. However in the J. League Cup match against Sagan Tosu, Tomiyasu was sent off for a second bookable offence, in a 1–1 draw. Two months later, on 13 July 2016, he made his league debut for the club, starting in the defensive midfield position in a 2–1 win against FC Tokyo. Since making his debut for the club, Tomiyasu became a first team regular for the side, playing in the defensive midfield position. It was reported on 26 September 2016 that he has become the second player in the league to be the fastest player at 12.436 km in. Following the club’s relegation to J. League 2, Tomiysu went on to make sixteen appearances in all competitions. At the end of the 2016 season, Tomiysu had his contract with the club.
In the 2017 season, Tomiysu became a first team regular for the side, playing in the centre-back position. He then scored his first goal for the club, in a 2–1 win against Roasso Kumamoto on 19 March 2017. Despite being absent from the first team, due to international commitment, Tomiysu continued to regain his first team place for the club for the rest of the season. He then helped Avispa Fukuoka three clean sheets in three matches between 29 July 2017 and 11 August 2017. Tomiysu later helped the club qualify for the J1 League Promotion Playoffs, having finished fourth place in the league. He helped the side beat Tokyo Verdy 1–0 to reach the semi–finals of the J1 League Promotion Playoffs. In the final of the J1 League Promotion Playoffs against Nagoya Grampus, Tomiysu played 90 minutes, as they drew 0–0 but saw Avispa Fukuoka unsuccessfully promoted to J. League One. At the end of the 2017 season, Tomiysu went on to make thirty–nine appearances and scoring once in all competitions.
It was announced on 8 January 2018 that Tomiyasu would be moving abroad for the first time in his career by joining Belgian First Division A side Sint-Truiden. He signed a three and a half year contract with the club, keeping him until 2021. Upon joining the club, Tomiyasu said: "I want to become a special player in Belgium." After spending months at training and recovering from an ankle injury, Tomiyasu made his Sint-Truiden debut for the club, coming on as a late substitute, in a 2–1 win against Royal Antwerp on 12 May 2018. This turned out to be his only appearance of the 2017–18 season.
In the 2018–19 season, Tomiyasu made his first start for Sint-Truiden and played the entirety of a 0–0 draw against Cercle Brugge in the opening game of the season. Since the start of the season, he became a first team regular for the side, playing in the centre-back position. Between 23 September 2018 and 30 September 2018, Tomiyasu kept three consecutive clean sheets in three matches. Having spent in the centre-back position since the start of the season, he played in the right–back position, which came against Zulte Waregem on 4 November 2018. Tomiyasu scored scored his first goal of the season on 25 November 2018 in a 4–2 win against Anderlecht. After spending January on international duty with Japan, Tomiyasu returned to Sint-Truidense on 9 February 2019, starting and playing the full 90 minutes in a 2–1 win against Waasland-Beveren. He continued to regain his first team for the side for the rest of the 2018–19 season. His performance received praise from the Belgian media. As a result, he won the club’s Player of the Year. In his second season at Sint-Truidense, Tomiyasu made 40 appearances and scored once in all competitions.
It was reported on 29 June 2019 that Bologna agreed a 9-million euro deal to sign Tomiyasu. The transfer move was confirmed on 9 July 2019 and becomes the second Japanese player to join the club after Hidetoshi Nakata. Upon joining the club, he said: "Impression that the defensive tactics are detailed. The striker level is also very high. I chose this team because I wanted to learn individual defense tactics. First I wanted to be on the pitch."
Tomiyasu made his Bologna debut, playing the whole game, in a 3–0 win against Pisa in the first round of the Coppa Italia. A week later he made his league debut, playing the full 90 minutes of a 1–1 draw against Hellas Verona, and was named Man of the Match for his performance. Having made three appearances, he was named August's Player of the Month. He started in the first league seven matches before suffering a hamstring injury in October that kept him out for a month. On 24 November, he made his return to the starting lineup in a 2–2 draw against Parma. Since joining the club, Tomiyasu quickly established himself in the starting eleven playing at right-back, and his performances impressed the Italian media and supporters alike. By the time the season was suspended because of the COVID-19 pandemic, he had made 20 appearances in all competitions. Tomiyasu remained an integral part of the club once the season resumed behind closed doors. He scored his first goal for Bologna in the 44th minute with his left foot, in a 5–1 loss against Milan on 18 July 2020. In a follow–up match against Atalanta, Tomiyasu suffered a hamstring injury and was substituted in the 74th minutes, as the club lost 1–0. After the match, it was announced that he would be sidelined for the rest of the 2019–20 season. Despite this, Tomiyasu finished his first season at Bologna, making 30 appearances and scoring once in all competitions.
Ahead of the 2020–21 season, Tomiyasu’s performances last season led to suggestions that he could be playing in the centre–back position. Tomiyasu soon recovered from his injury and regained his first team place, playing in the centre-back position. In a match against Sassuolo on 18 October 2020, he scored an own goal after a cross from Giorgos Kyriakopoulos, leading to the winning goal for the opposition team. In December, Tomiyasu began playing as right-back for the rest of the season, though he occasionally played as a left-back and centre-back. This was due to his struggles playing as centre-back, resulting in criticism by the Italian media. His performances began to improve as a result of the tactical change. Tomiyasu scored his first goal of the season in a 2–2 draw against Atalanta on 23 December. Two weeks later on 6 January 2021, he scored his second goal of the season, scoring from a header, in a 2–2 draw against Udinese. However, Tomiyasu suffered a calf injury that saw him out for two weeks. He made his return to the starting line–up two weeks later than expected on 14 March against Sampdoria, starting in a 3–1 win. His return was short–lived when he suffered a muscular problem against Inter Milan on 4 April. After being sidelined for a month, he made his return to the starting line–up on 2 May against Fiorentina and played 76 minutes before being substituted, in a 3–3 draw. By the end of the season, he had made 33 appearances and scoring two times in all competitions.
Ahead of the 2021–22 season, Tomiyasu was linked with a move to Premier League club Tottenham Hotspur and Atalanta. Amid to the transfer speculation, he made his only appearance of the season against Atalanta, coming on as an 81st minutes substitute, in a 0–0 draw on 28 August 2021.
On 31 August 2021, Tomiyasu joined Premier League side Arsenal on a four year deal, with an option for a fifth. The transfer was variously reported as £15.5million, £16 million and £17 million. Upon joining the club, both manager Mikel Arteta and technical director Edu commented about the player, describing him as "important member of the squad" at Arsenal.
Having previously played for Japan U14 and Japan U15, Tomiyasu was called up to the Japan U16 for the first time in March 2013 ahead of the Montaigu Tournament. He participated in the tournament, as the U16 side finished seventh place. In August 2014, Tomiyasu was called for Japan U16 ahead of the AFC U-16 Championship in Thailand. He made two appearances in the tournament, as Japan U16 were eliminated in the quarter–finals.
In July 2014, Tomiyasu was called up to the Japan U17 for the first time. He participated in a number of matches for the side throughout 2015.
In June 2015, Tomiyasu was called up to the Japan U18 squad for the Panda Cup. He played two times in the tournament, as the U18 side won the trophy, finishing first place. In March 2016, he was called up to the Japan U-19 squad for the first time. Six months later, he was ahead of the AFC U-19 Championship in Bahrain. He played his first match of the tournament, where he helped the U19 side win 3–0 against Yemen U19. Tomiyasu scored his first goal of the tournament, in a 3–0 win against Qatar U19 on 20 October 2016. He helped the Japan U19 reached the final after beating Vietnam in the semi–final. Tomiyasu started in the final against Saudi Arabia U19 and played 120 minutes; which resulting Japan U19 won 5–3 on penalties. During the AFC U-19 Championship tournament, he helped the Japan U19 side keep all six clean sheets.
In May 2018, Tomiyasu was called up to the Japan U21 for the first time ahead of the Toulon Tournament. He went on to make four appearances for the side, as they were eliminated in the Group Stage.
In June 2021, Tomiyasu was named in the Japan squad for his first Olympictournament, this time on home soil. He previously expressed his interest in playing at the tournament. Prior to the start of the Olympics, Tomiyasu was featured three out of the four friendly matches for the national side. Along the way, he suffered ankle injury, but it did not affect his chances to be in the Olympics squad. Tomiyasu made his debut in the tournament against France Olympic team on 28 July 2021 and started the whole game to help Japan win 4–0. He made two more appearances for the Olympics team, including a 2–0 loss against Mexico Olympic team in the bronze medal match.
On 30 August 2018, Tomiyasu received his first international call-up from the Japan national team for the Kirin Challenge Cup 2018. It wasn’t until on 12 October 2018 when he made his Japan debut, starting the whole game, in a 3–0 win against Panama. Tomiyasu became the first teenager to start in the senior team since Ryo Miyaichi. A month later on 16 November 2018, he made his second appearance for the national side, in a 1–1 draw against Venezuela.
In December 2018, Tomiyasu was re-called to the Japanese squad for the 2019 AFC Asian Cup. He made his tournament debut for the national side, starting the whole game and helped Japan win 3–2 against Turkmenistan. He helped Japan keep a clean sheet by beating Oman 1–0 win to advance to the knockout stage. He then scored his first goal for the national side, scoring from a header, in a 1–0 win against Saudi Arabia to reach the semi–finals. Tomiyasu later played two more matches of the tournament, which saw the national side reaching the final for the first time since 2011. In the AFC Asian Cup final against Qatar, he started and captained the side, as they lost 3–1, finishing as runner–up in the process.
Following the conclusion to the AFC Asian Cup tournament, Tomiyasu was called up to the squad ahead of the Copa América in Brazil. He started all three matches, playing in the centre–back position, as they were eliminated in the Group Stage. He later played three matches of 2019, helping the national side keep three clean sheets.
Almost a year absent, Tomiyasu was called up to the Japan squad on 6 October 2020. He started three out of the four matches for the national team by the end of the year.
Style of play
Playing in either the right–back or centre–back positions, Tomiyasu is known for being well structured physically, as well as his ambidexterity and speed.
His performance at Sint-Truiden was impressive that Voetbal Nieuws that they named him "The Best Eleven of Foreign Players Who Have Left from the Jupiler League". Former teammate Pol García praised Tomiyasu for his attitude, while former Italy international defender Cristian Zaccardo praised his strong and energetic performances.Bologna’s technical coach Emilio De Leo said about Tomiyasu’s performances, saying: "He has the ability to read and manipulate time and space in a modern way." The club manager Marco Di Vaio agreed, saying: "Tomiyasu immediately impressed us because he is very good with his feet and knows how to adapt to all defense roles." National Italian newspaper Corriere dello Sport praised Tomiyasu’s performance, saying: "He is a treasure. The key to reinforcing Bologna".
Manuel Minguzzi, a reporter for Tuttobologna, said about his performance: "Fans can always expect maximum professionalism and commitment from Tomiyasu. As a full back he did very well, while as a central he made some mistakes, but in Serie A it is quite normal because adaptation is needed. Tomiyasu also possesses great qualities when building the game. I was very struck by the fact that in the first year of Serie A he immediately became the protagonist. He had been taken as a central-defender but was often used as full-back offering both phases of play. As soon as he arrived he became an idol. The Japanese market is always very active on social networks and Bologna has expanded its popularity thanks to Tomiyasu." Former Japan manager Alberto Zaccheroni praised manager Siniša Mihajlović for using Tomiyasu regularly in the first team, saying: "He was good but not malicious, Mihajlovic did a great job making him play a full-back year, in less risky areas, and then use him as a central player after gaining experience."
Tomiyasu has two sisters. He was planning to do swimming to follow his sisters before switching to football instead. In his first Bologna’s press conference, Tomiyasu said he began to learn Italian and asked the media to call him Tomi. By February 2020, Italian media Corriere Di Bologna reported that Tomiyasu already spoke Italian.
Growing up, Tomiyasu said he idolised Javier Mascherano. Tomiyasu said that he wanted to be a footballer. Tomiyasu spoke out about his life in Italy in the COVID-19 pandemic and while the season was suspended, he exercised daily. On 12 May 2020, his former club, Avispa Fukuoka expressed their graditute to Tomiyasu after he donated 1,000 masks to the club’s academy. The following month, Bologna revealed that the players and staff members agreed to give up a month’s salary.
^"金沢vs福岡 試合記録" (in Japanese). Web Gekisaka. 8 August 2015. Retrieved 19 April 2020. "福岡vs磐田 試合記録" (in Japanese). Web Gekisaka. 15 August 2015. Retrieved 19 April 2020. "町田vs福岡 試合記録" (in Japanese). Web Gekisaka. 14 October 2015. Retrieved 19 April 2020.