Over the past decades, neutrino physics has emerged as a dynamic and fascinating field in particle physics. The experimental observation of the oscillation mechanism, possible if neutrinos have non-zero mass, represented evidence of physics beyond the Standard Model. Nonetheless, several properties of these mysterious particles still need to be addressed, such as clarifying the presence of charge-parity violation in the leptonic sector and validating the three-neutrino flavor paradigm. By ensuring high-precision measurement of the oscillation parameters, worldwide next-generation neutrino experiments are being built to eventually answer these open questions and bring neutrino physics into a precision era. KM3NeT is a water Cherenkov neutrino telescope currently under construction in two detection sites in the Mediterranean Sea: ARCA, pursuing astronomical searches, and ORCA. By studying the oscillations of the atmospheric neutrino flux passing through the Earth, ORCA’s primary physics goal is an early measurement of the neutrino mass ordering. Additionally, thanks to the unprecedentedly accessible neutrino statistics, it will have high sensitivity to the observation of the least known tau neutrino. Exploring its appearance via oscillation allows to test the standard three-neutrino flavors paradigm through the tau neutrino normalization measurement. Thanks to its modular structure, high-level physics studies are possible from the detector installation phase. After describing the advantages and challenges intrinsic to such an evolving detector configuration, I will present the first measurement of the tau neutrino normalization performed by exploiting the first longest data sample collected with 6 Detection Units (equivalent to 5% of the final geometry), from January 2020 to November 2021.