ΔE 18.1, loose: different enough that you should pick on purpose. Kossite Flesh Wash is a little darker, much more muted, warmer than Seraphim Sepia.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Kossite Flesh Wash is a little darker, much more muted, warmer than Seraphim Sepia.
The same difference applies the other way round: Seraphim Sepia is a little lighter, much more saturated, cooler.
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 Seraphim Sepia on the colour wheel See Kossite Flesh Wash on the colour wheel
All matches: Seraphim Sepia equivalents · Kossite Flesh Wash equivalents