This chapter concludes the book by highlighting human security, a people-centred approach that underscores dignity, solidarity, and perpetual peace. It highlights the role of ‘drifters,’ individuals who cross borders and connect communities, as agents of mutual learning between peoples. Three major case studies illustrate the emergence of this approach in Japan’s development cooperation. The first concerns Nikkei youth programs for young ethnic-Japanese students in Brazil and other Latin American countries, through which they rediscovered their hybrid identity and built transnational networks. Rooted in Japan’s emigration policy, these initiatives evolved into dynamic cultural exchange and leadership development. The second case explores environmental cooperation between Minamata in Japan and the Amazon Basin in Brazil, prompted by mercury pollution in both regions. Japanese citizen-scientists like Akagi Hirokatsu transferred analytical methods. Finally, collaboration between peace museums in Okinawa and Cambodia reveals how shared memories and reflections on war and violence could nurture people’s empathy and peace education. The Cambodian case ends with the successful water supply project known as the ‘Miracle of Phnom Penh’. Across these experiences, a new, horizontal, participatory, and dialogical modality of Japan’s cooperation emerges. Collaboration for human security has been taking shape in the middle of bilateral cooperation for nation-building.