Martial arts are increasingly promoted as interventions for youth in high-risk, socioeconomically marginalized areas. While existing literature has focused on psychological outcomes such as self-regulation, or sociological themes like identity transformation, few studies have examined the micro-social mechanisms through which martial arts may prevent criminal involvement. Drawing on 52 qualitative interviews with coaches and young practitioners across Swedish martial arts clubs located in so-called "vulnerable areas," this study explores how sparring functions as a site for relationship-building, emotional co-regulation, and social repair. Using the concept of rough-and-tumble play (RTP) from developmental psychology, the paper analyzes how structured physical contact within martial arts can produce trust, care, and affiliation-qualities central to social cohesion and crime prevention. Findings show that martial arts clubs operate as "communities of care," where ethical forms of masculinity, credible role models, and embodied rituals of mutual respect counter the appeal of gang recruitment. However, the potential of martial arts is contingent on context; when RTP principles are violated-through unsafe environments or toxic sparring cultures-the same practices can backfire, harming trust and reinforcing alienation. The study contributes to criminological theory by foregrounding embodied interaction as a core mechanism in desistance-supportive environments and calls for closer attention to the relational infrastructures that make such interventions work.