In, Hiroshima Toyo Carp selected him in the third round. He missed time his first year in the minors with injuries to his elbow and toe and a norovirus. He hit.277 with 21 steals in the minors in 2010. He was called up to Hiroshima later in the year. In his debut, he pinch-hit for Ren Nakata and was retired by Marc Kroon. His first hit came off Takehiko Oshimoto, singling as a pinch-hitter for Keisuke Imai. He was 3 for 19 with two walks, a steal, a run and a RBI in 14 games for the Carp in 2010. His first NPB homer came off Tomokazu Ohka on April 19, 2011. He became Hiroshima's starting center fielder that year, unseating Soichiro Amaya and Masato Akamatsu. He hit.241/.319/.359. He was 4th in the Central League with 105 strikeouts. In 2012, he batted.247/.353/.353 with 14 steals in 20 tries, splitting CF with Amaya and Akamatsu and backing up Jun Hirose in RF. By 2013, he was back in a starting role in center, usually hitting leadoff or second. He produced at a.273/.376/.425 clip with 85 walks, 14 home runs, 82 runs and 29 steals but was caught 15 times. He won a Gold Glove after fielding.992 ; Sho Aranami and Hisayoshi Chono were the other CL Gold Glove winners. He made the CL leaders in runs, doubles, triples, steals, caught stealing, walks, strikeouts and OBP. He made his first CL All-Star team. Early in 2014, he became the Carp's regular #3 batter. He hit.310/.419/.491 with 30 doubles, 5 triples, 19 home runs, 100 walks, 106 runs and 26 steals in 37 tries. He fielded.993 and this time also had 8 outfield assists. He was the 22nd player in NPB history to reach triple-digits in walks. He finished the year all over the CL leaderboards: 9th in average, 2nd in OBP, 8th in slugging, 3rd in OPS, tied for first in runs, 8th in hits, tied for 6th in doubles, tied for second in triples, tied for 9th in homers, 3rd in steals, 2nd in caught stealing, led in walks while falling to a tie for 9th in whiffs and 5th in total bases. He won his second Gold Glove and made the Best Nine as one of the CL's top three flyhawks. He got three second-place votes for the 2014 Central League Most Valuable Player Award. In the 2015 season, he struggled, hitting.249/.361/.413. He still had 28 doubles, 19 homers and 94 walks, but his steals were down, his strikeouts were up and his average was obviously down. He still tied Kosuke Fukudome for 9th in OBP, was third in runs, tied Gomez and Yoshitomo Tsutsugo for 7th in doubles, tied Brad Eldred for 6th in home runs and led in walks again. He fielded.996, with 273 putouts, 6 assists and one error. He won his third straight Gold Glove, joining Oshima and Fukudome. Maru hit.291/.389/.481 with 30 doubles, 8 triples, 20 homers, 23 steals in 32 tries, 98 runs, 90 RBI and 84 walks in 2016. He was 3rd in the CL in runs, 10th in slugging, 5th in hits, was second in doubles, tied Seiya Suzuki for second in triples, missed the top ten in homers by two, was 7th in RBI, placed 5th in steals and was third in walks. He won a Gold Glove and joined Suzuki and Tsutsugo in the Gold Glove outfield. For the 2017 season, his batting line was.308/.398/.505. The multi-tool threat had 109 runs, 35 doubles, 23 home runs, 83 walks and 92 RBI while his steal total was down a bit. He led the CL in runs, tied José López for the most hits, was 4th in doubles, ranked 8th in circuit clouts, was third in RBI, was 5th in average, was 4th in walks, was just behind Tanaka in OBP and was 7th in slugging. He won another Gold Glove, made another Best Nine and won the 2017 Central League Most Valuable Player Award., with 196 of 286 first-place votes and 1,134 vote points to 381 for runner-up Kazuki Yabuta. Maru was again dominant in 2018 despite missing time with a hamstring injury:.306/.468/.627, 39 HR, 130 BB, 109 R, 97 RBI,.996 fielding percentage. He was second in runs, second in homers, 4th in RBI, first in walks, first in OBP, second in slugging and first in OPS. He joined Suzuki and Soto in getting the Best Nine honors and won another Gold Glove. He won the 2018 CL MVP award, with 241 first-place votes and 1,314 vote points. He was the first repeat MVP in the CL since Alex Ramirez 9 years prior and the first Japanese native to repeat as CL MVP since the legendary Sadaharu Oh in the late 1970s. He became a free agent at year's end. On December 11, 2018, he signed 5-year, 2,55 billions yen with Yomiuri Giants.
