Star-cluster and galaxy formation simulations are now in the era of star-by-star simulations. SIRIUS project aims to simulate star-cluster and galaxy formation resolving individual stars. By resolving individual stars, we investigate the formation and evolution of star clusters and galaxies, especially the role of massive stars there. 

For this purpose, we develop ASURA+BRIDGE, a state-of-the-art code based on an N-body/SPH code, ASURA, and a tree-direct hybrid N-body code, PeTar. PeTar includes an algorithm for hard binaries, enabling the integration of stellar orbit without gravitational softening. This code can simulate the dynamical evolution of stellar systems embedded in the surrounding gas.