Overview of KAGRA: KAGRA science

KAGRA is a newly build gravitational wave observatory, a laser interferometer with 3 km arm length, located in Kamioka, Gifu, Japan. In this paper, one of a series of articles featuring KAGRA, we discuss the science targets of KAGRA projects, considering not only the baseline KAGRA(current design) but also its future upgrade candidates (KAGRA+) for the near to middle term (similar to 5 years)