As China is becoming more autocratic in recent years, the cyberworld, based on the widely popularised access to the Internet, has become the new battlefield for political propaganda. The young adolescents who were previously difficult to target with conventional didactics have become the main objects. The entry of the Central Committee of the Communist Young League to the website: Bilibili, at the beginning of 2017, is a clear sign of the determination of the national leadership in turning the self-entertained ACGN (Animations, Comics, Games and light Novels) fans into the proactive agents of the Party and the State. To figure out the effects of such an action, this research selects 15 most-viewed videos released by three national media on Bilibili for textual and multi-modal discourse analyses. In addition, as danmus (弹幕, also translated as bullet chats) is a unique function of Bilibili, this research also summarises their characteristics and explores the rich discourses with the assistance of the programming language Python. This research finds out that the national leadership is leading the refinement of nationalism on Bilibili. Certain well-developed online grassroots nationalism is selected and incorporated into the official narrative, and the idea of “love the Party” and the dream-chasing struggle of rural grassroots are being included in the umbrella concept of nationalism as new components. With clear acknowledgement of the official natures of the videos, the recipients of such refined nationalism, while keeping their identity as “ACGN fans”, begin to pick up the identity of “little pink”, namely, the advocators of the Party and the Country. Furthermore, the widely-popularised Internet and its communication power have greatly accelerated the interaction between nationalism (the state-led mainstream culture) and ACGN contents (a representative subculture/popular culture). In particular, nationalism is being diffused through subcultural ways recreationally, which further blurs the boundary between mainstream culture and subculture, complying with the overall trend of cultural convergence in the 2020s. This research sets a typical example of investigating the mutual effect between politics and culture in the digital era. The research results may supplement our understanding of the ever-evolving relationship between mainstream culture and subculture in the context of contemporary China, where the political situation is experiencing drastic changes.