<p>This study reports the preliminary findings of a randomized controlled trial evaluating the early stage outcomes of <i>TheraBuddy</i>, a web-based interactive visual novel designed to primarily promote active bystander intervention in bullying situations and, indirectly, to support social-emotional health among preadolescents and adolescents. Participants were 138 students aged 10–16 years recruited from six schools in Ankara, Türkiye, and randomly assigned to either an intervention group (<i>n</i> = 71) or a waitlist control group (<i>n</i> = 67). While the full trial included four measurement points over a three-month period, this report focuses on data from a pretest and a one-month posttest. Students in the intervention group were invited to engage with the game during the intervention period; by the end of the first month, 43% (31/71) had completed at least 10% of the game. A mixed-design ANOVA revealed a marginal time x condition interaction for active bystander intervention (F(1,136) = 2.97, <i>p</i> = .08, η² = 0.02), with mean scores in the intervention group increasing from M = 54.59 (SD = 16.97) at pretest to M = 60.87 (SD = 12.28) at one-month posttest, compared to a smaller increase in the waitlist control group from M = 54.73 (SD = 14.15) to M = 57.13 (SD = 12.55). For social-emotional health, the time × condition interaction was not significant (F(1,136) = 1.35, <i>p</i> &gt; .05, η² = 0.01), with the intervention group showing stable mean levels (M = 121.49, SD = 18.07 at pretest; M = 121.63, SD = 15.91 at posttest), while the waitlist control group showed a decline from M = 118.23 (SD = 17.81) to M = 115.88 (SD = 18.05). These findings should be interpreted cautiously given the short follow-up period and variable engagement levels. Overall, the results suggest that a theory-driven visual novel game may produce small, early-stage changes in bystander-related attitudes under naturalistic usage conditions. Implications for school-based bullying prevention efforts are discussed.</p>