I have studied transient events of dwarf novae and low-mass X-ray binaries by
multi-wavelength observations and numerical simulations. They are well observed and it
is known that both of them show outbursts by thermal-viscous instability. However,
recent development of telescopes and satellites detected new kinds of outbursts and
short-term variability that cannot be explained by the standard model. In this seminar,
I introduce a few of my research works and discuss how to approach the unsolved issues
in this field. I also talk about future observations with XRISM and other telescopes
and future simulations works for black-hole binaries.