[1] Whilst a student at Waseda University, Yoshioka founded Peace Boat in 1983 to foster grassroots dialogue and people-to-people reconciliation between Japan and other Asian countries, during a period of tension and hostilities in the region.
Yoshioka has led the organization of these voyages, as well as initiatives such as peace education for youth from conflict zones and post-conflict countries, and Northeast Asian people's dialogues.
Yoshioka is a founding member of the UN-initiated Global Partnership for the Prevention of Armed Conflict (GPPAC) International Steering Group and head of its Northeast Asia Secretariat.
He was nominated for the Nobel Peace Prize in 2008 for leading the Global Article 9 Campaign to Abolish War.
[3] After the 2011 Tōhoku earthquake and tsunami, Yoshioka established the Peace Boat Disaster Relief Volunteer Centre (PBV), which has dispatched more than 14,000 volunteers to the stricken region and helped to rebuild devastated neighborhoods, as well as working on Disaster Risk Reduction through training young leaders worldwide.