This cluster-randomized pilot trial will evaluate the preliminary effects and feasibility of adding an indirect contact component to a school-based mental health literacy (MHL) lesson for 5th-grade students in a public elementary school in Tokyo, Japan. Four 5th-grade classes (approximately 150 students in total) will be randomized by class (two classes per arm). All students will receive a 45-minute lesson that includes an animated video and educational slides. In the intervention arm, teachers will additionally introduce a short story about a well-known soccer player who experienced and recovered from a mental health condition, serving as an indirect contact element. The control arm will receive the standard lesson without this component.

Students will complete questionnaires at baseline (T1), immediately after the lesson (T2), and 2-3 months later (T3). The primary outcome is vignette-based social distance toward a peer with mental health problems. Secondary outcomes include mental health knowledge, help-seeking intentions, perceived need for help, intended sources of help. As a pilot study with only four clusters, the trial is not powered to detect small effects; findings will be used to estimate effect sizes and assess feasibility for a future larger-scale trial.

This study investigates whether incorporating an indirect contact component into an existing school-based mental health literacy (MHL) program enhances reductions in stigma-specifically vignette-based social distance-among elementary school students. Indirect contact is implemented through a teacher-delivered story describing the lived experience and recovery of a well-known soccer player who publicly disclosed his mental illness. This approach aims to promote empathy, reduce negative stereotypes, and strengthen intentions to seek or recommend appropriate help.

The study uses a cluster-randomized parallel-group design, with four 5th-grade classes assigned (2:2) to either the intervention or control condition. Both groups receive a standardized 45-minute MHL lesson including an animated educational video and discussion materials. The intervention arm additionally receives the indirect contact component within the same 45-minute period. The lesson is delivered by classroom teachers.

Assessments occur at three time points:

• T1 (baseline): before the lesson
• T2 (post-test): immediately after the lesson
• T3 (follow-up): 2-3 months after the lesson

The primary outcome is a 5-item social distance scale based on a vignette ("A-san") describing symptoms consistent with depression. Secondary outcomes include:

• mental health knowledge
• intentions to support a friend with similar problems
• perceived need for help
• personal help-seeking intentions
• intended help-seeking sources

Because this is a pilot trial, the goals are to evaluate feasibility (recruitment, retention, acceptability, implementation fidelity) and to estimate preliminary effect sizes to inform sample size calculations for a future fully powered cluster randomized trial. After T3 data collection, students in the control arm will be offered an educational supplement that includes the indirect contact story.

Inclusion Criteria:

• Students enrolled in 5th grade at one of the eight participating public elementary schools in Kanazawa, Japan.
• Aged 10-11 years old.
• Passive consent obtained from guardians; verbal assent obtained from children.
• Able to complete self-report questionnaires.

Exclusion Criteria:

• Students whose parents/guardians opted out of the study.

Note: Students who were absent on the day of the pre-test (T1) were excluded from the analysis population but not from the initial study cohort.

Because this study involves minors in a school-based setting and includes sensitive educational and mental health-related information, individual participant data cannot be shared. Disclosure of such data could risk re-identification even after de-identification procedures. In accordance with ethical guidelines and institutional policies, IPD will not be made available.

Students were not informed whether they were in the intervention or control class. Classroom teachers delivering the lesson were aware of group assignment.