This article explores the reasons behind the success of user-generated content (UGC) advertisements on Bilibili, which is one of China’s most significant video-sharing social media sites, with a core focus on East Asian pop culture. Additionally, Madoka Magica is a well-known Japanese animation about magical girls. There are two derivative games based on it. By using diffusion of innovation theory and content analysis method, this article takes UGC advertisements of Madoka Magica’s mobile games as windows to investigate how early adopters (influencers) motivate early majority adopters (their followers) to play the game. Moreover, this paper also addresses three types of bullet chats in this kind of video to further explore followers’ interaction with the influencers and reasons for the success of its marketing method. Bullet chats are a unique way to observe target consumers’ reaction to the advertisements. The author found that word-of-mouth marketing, the right audience and influential people are important factors for the success of UGC advertising. Besides, this marketing strategy is not limited to the marketing of mobile game advertisements, but can also be used for the marketing of other products. However, the prerequisite for this marketing method to be effective is that the advertised product or service has good quality