This study delves into the mechanisms by which avatar customization in Metaverse gaming enhances user immersion, a phenomenon previously established but not fully understood. We adopted thematic analysis to explore the specific effects of avatar customization. The research found that avatar identification impacts immersive usage through emotional response, and higher avatar aesthetics strengthen this path. Moreover, the noteworthy aspect is that, in contrast to the transient identification with the avatar, avatar attachment serves as a long-term and enduring emotional connection (like keeping a pet), thereby playing a significant moderating role in improving immersion. The paper contributes to existing research by clarifying the diverse facets of avatar attachment under the context of Metaverse gaming. Moreover, it provides actionable insights for virtual world designers to optimize customization features and foster deeper experiences among users.