This blog gives a guide to study Economics in SILS, Waseda university. SILS gives you great chances to study several fields. On another front, if you'd like to select to study Economics, SILS offers only a few subjects of Economics.
HOWEVER, your situation is not so awful because SILS provides basic classes of Economics such as Microeconomics & Macroeconomics. Since Economic principle is simple, and the theory is constructed logically and consistently from the simple principle. So, once you understand the principle and the logical deductions, it is not so difficult to study Economics regardless of your department. I'm happy if this blog helps you study Economics.
HOWEVER, your situation is not so awful because SILS provides basic classes of Economics such as Microeconomics & Macroeconomics. Since Economic principle is simple, and the theory is constructed logically and consistently from the simple principle. So, once you understand the principle and the logical deductions, it is not so difficult to study Economics regardless of your department. I'm happy if this blog helps you study Economics.