This study tried to identify few possible industry sectors in different BIMSTEC (Bay of Bengal Initiative for Multi Sector Technical and Economic Co-operation) member countries, which have the potential to attract foreign direct investment (FDI) in general and Japanese investment, in particular. As capital markets of most of the BIMSTEC countries (except Thailand and India) are not properly developed to attract and manage portfolio fund, here by 'investment', we mean 'foreign direct investment' (FDI) only. The paper is broadly divided into five parts. Part I, deals with the background of this sub-regional grouping and analyzes the rationale behind identifying Japan as the natural ally of BIMSTEC. Part II explains the methodology and explores the theoretical framework of the study. Part III explores, from macro perspectives, the possible outward investment opportunities and challenges faced by Japanese investors. Part IV does the same by analyzing country specific information of the BIMSTEC member countries and in Part V, explores alternative financial source in the huge current account surplus of major East Asian countries. Modalities of another sub-regional initiative - the Greater Mekong Subregion (GMS) program are also documented as a case study.