[5] In May 2016, Sagan Tosu announced that Tagawa were among four players to be registered with the top team (second-type registration).
[7] In July 2016, he was described by the youth reporter of Web Gekisaka, saying: "His height of 181 cm is eye-catching, but his strength is his speed, running 50 meters in the low six seconds.
[9][10] Tagawa's first appearance in the Sagan Tosu's first team was on 22 October 2016 as an unused substitute, in a 3–2 win against Kashiwa Reysol.
[12] Tagawa made his debut on 5 March against Kawasaki Frontale, when he replaced Takamitsu Tomiyama in a 1–1 draw.
[13] Ten days later on 15 March 2017, Tagawa made his first start for the club and set up the opening goal of the game, in a 2–2 draw against Albirex Niigata in the J.League Cup.
[17] Since returning from his international duty, Tagawa received playing time as the club's main striker.
[24] However, Tagawa suffered a goal drought that eventually saw him demoted to the substitute bench, due to the arrivals of Fernando Torres and Mu Kanazaki.
[29] He made his debut for the club, coming on as a substitute, in a 0–0 draw against Kawasaki Frontale in the opening game of the season.
[31][32] He then returned from injury, playing for FC Tokyo U23, coming on as a late substitute, in a 3–0 loss against Fujieda MYFC on 27 July 2019.
[34] He made his first team return for FC Tokyo, starting the match, in a 3–0 loss against Ventforet Kofu in the third round of the Emperor's Cup on 14 August 2019.
[37] It wasn't until on 30 November 2019 when Tagawa scored his first league goal for the club, in a 1–1 draw against Urawa Red Diamonds.
[40][41] Once the season resumed behind closed doors, Tagawa made his first appearance, coming on as a 28th-minute substitute, in a 1–0 win against Kashiwa Reysol on 4 July 2020.
[42] However, during a match against Yokohama F. Marinos on 12 July 2020, he suffered a dislocated shoulder to win a penalty and was substituted as a result, as the club won 3–1.
[44] It wasn't until on 5 September 2020 when he made return from injury, starting a match, in a 1–0 win against Oita Trinita.
[63] Upon joining the Jam Tarts, he apologised to FC Tokyo's supporters for leaving the club and stated that it was difficult to turn down a move to Europe.
[64] Tagawa made his debut for Hearts, coming on as a 69th-minute substitute, in a 2–0 win against St Johnstone in the opening game of the season.
[65] On 17 August 2023, he made his UEFA Europa League debut against Rosenborg as a substitute and helped the club win 3–1 to advance to the next round.
[69] Upon returning from injury, he found his first team opportunities limited, with Lawrence Shankland and Kenneth Vargas preferred.
[70] After suffering a concussion, Tagawa was linked a move back to Japan, but he eventually stayed at the club for the rest of the 2023–24 season.
[78] In March 2015, Tagawa was called up to the Japan U17 squad for the Sanix Cup International Youth Soccer Tournament.
[81] A year later, he was called up to the Japan U17 squad for the Sanix Cup International Youth Soccer Tournament.
[91] In August 2016, Tagawa was called up to the Japan U19 squad for the SBS Cup International Youth Soccer.
[95] Tagawa played two times in the group stage, including scoring his first goal in the tournament, in a 5–0 win against Iraq U19 on 25 October 2018.
[101] Tagawa made another appearance in the tournament, coming on as a late substitute, in a 1–0 loss against Venezuela U20 in the last sixteen of the 2017 U-20 World Cup.
[107] However, during a match against Italy U20, he suffered a hamstring injury and was substituted in the 22nd minute, as Japan U20 drew 0–0 and advanced to the knockout stage.
[110] Tagawa started two matches for the U21 side, including setting up a goal for Ko Itakura, in a 1–0 win against Thailand U23.
[121] In December 2019, Tagawa was called up to the Japan squad for the first time ahead of the EAFF E-1 Football Championship.