"Tsubame" is a university-built small satellite mission that measures polarization of hard X-ray photons (30-100 keV) from gamma-ray bursts (GRB) using azimuthal angle anisotropy of Compton scattering. The satellite is intended for a piggy-back launch on the H-IIA rocket. It uses Control moment gyros to quickly orient itself to GRBs within 15 seconds from triggers. We are now developing the engineering model of the two detector systems on Tsubame, the polarimeter and the bust monitor. In this paper, we present an overview of the Tsubame mission, and detail of development of engineering model of our polarimeter and burst monitor.