<p>With the rapid development of digital media and changing social attitudes, sexuality education has entered the public discourse in China. However, current research largely focuses on knowledge dissemination and behavioral interventions, often neglecting individuals’ lived experiences and narrative expressions. This study addresses this gap by using corpus-assisted discourse studies (CADS) to examine user comments under a sexuality education video on Bilibili, China’s leading video platform for young people. Using Latent Dirichlet Allocation (LDA) topic modeling, collocation analysis, and Bronfenbrenner’s Ecological Systems Theory (EST), the study identifies four recurring themes: masculine curiosity and feminine shame, family and school as dual arenas of Sexuality, peer support and gendered prejudice, sexual enlightenment and trauma in the digital sphere. Findings reveal the absence and interplay of sex education at multiple systemic levels, illustrating how young people are actively exploring sexual knowledge amid institutional silence and challenging traditional social taboos through digital media platforms. This research advances theoretical understanding of sexuality education discourse in China and offers practical insights for policy and curriculum development.</p>