Prof. Ohtsuki has been engaged in international collaboration with Prof. Kalle Parvinen at the University of Turku, Finland, on theoretical studies of the evolution of dispersal. They are trying to unveil the evolutionary reasons why organisms disperse their offspring despite several costs associated with it, by combining evolutionary dynamics and game theory. Both scientists are long-term research collaborators to each other, and through mutual visits, Prof. Parvinen has become very familiar with Japan, and Prof. Ohtsuki, in turn, has become a big fan of Finland.