ΔE 26.3, loose: different enough that you should pick on purpose. Seraphim Sepia is noticeably lighter, cooler than Soft Tone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Seraphim Sepia is noticeably lighter, cooler than Soft Tone.
The same difference applies the other way round: Soft Tone is noticeably darker, warmer.
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 Soft Tone on the colour wheel See Seraphim Sepia on the colour wheel
All matches: Soft Tone equivalents · Seraphim Sepia equivalents