He won his first BWF World Tour title at the 2023 Indonesia Masters Super 100 II.

He reached the finals of a senior international tournament for the first time at the Osaka International in 2019, finishing runner-up to countryman and former Saitama Sakae High School teammate Koki Watanabe.

Obayashi won his first BWF World Tour title at the Indonesia Masters Super 100 II in 2023.

That year, he also reached the finals at the Vietnam Open and won two more International Challenge-level tournaments, including the inaugural Saipan International after winning the final against top-seeded Jeon Hyeok-jin.

Obayashi later achieved notoriety for his upset victory over Anders Antonsen when making his Super 500-level debut at the 2023 Japan Masters, where he ultimately reached the semifinals before losing to world no.