ΔE 7.8, close: similar, with a visible difference side by side. Dark Sea Grey is a little lighter, more muted than IJN Gray (Sasebo Arsenal).
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Dark Sea Grey is a little lighter, more muted than IJN Gray (Sasebo Arsenal).
The same difference applies the other way round: IJN Gray (Sasebo Arsenal) is a little darker, more saturated.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See IJN Gray (Sasebo Arsenal) on the colour wheel See Dark Sea Grey on the colour wheel
All matches: IJN Gray (Sasebo Arsenal) equivalents · Dark Sea Grey equivalents