[2] Having officially joined the team in early 2023, he featured in a friendly against Hokushinetsu Football League side Fukui United on 26 February, where he played as a left-back, as opposed to his usual central midfield role.
[7] His professional debut came two months later, playing in Cerezo Osaka's 4–0 J.League Cup loss to Kyoto Sanga, coming on as a late second-half substitute for Kakeru Funaki.
[2] In June of the same year, he featured in the 5–0 Emperor's Cup win against Cento Cuore Harima, before suffering a knee injury which kept him out for a month.
[8] Osako was first called up to the Japan under-15 side in March 2019 as part of the "04 group" - players born in 2004 - in preparation for the 2021 FIFA U-17 World Cup.
[12][13] He scored once against Malaysia as Japan finished top of their group, however due to the COVID-19 pandemic, the 2020 AFC U-16 Championship, as well as the 2021 FIFA U-17 World Cup, was cancelled.