As of 2025, Haynes has not released a dedicated manual for the 125cc Gixxer in English (they focus on 600+ cc models). Your best bet is the OEM Suzuki manual.
The GSX-R125 (produced from 2017 onwards across Europe, Asia, and South America) is a single-cylinder, liquid-cooled, 124.4cc fuel-injected engine. While it is mechanically simpler than a four-cylinder 600cc bike, it has nuances unique to the platform. gsx r125 service manual