Since you are looking for (Version Originale Sous-Titrée Français), the OVA (Original Video Animation) is the most common format found with French subtitles. It consists of a few episodes that serve as an introduction to the much longer and more detailed manga by Ryuta Amazume .
: Most reviewers note that despite the explicit themes, the core of the series is the developing bond between the protagonists. It treats BDSM as a medium for communication rather than just a fetish, focusing on the vulnerability required to share one's desires. Nana to Kaoru VOSTFR
L’œuvre insiste lourdement sur le respect des limites. Kaoru demande systématiquement la permission (via un système de collier "Yes/No"). C’est une leçon de maturité rare dans le manga adolescent. Regarder Nana to Kaoru en VOSTFR permet de saisir des formulations japonaises très précises sur le consentement ("Yatte ii ?" vs "Yarou ka ?"). Since you are looking for (Version Originale Sous-Titrée