I haven’t read the light novels but I think the first season ends at the end of the second volume as the penultimate chapter is “Balsam and Woodsorre”.

There are 12 English translated and 15 Japanese novels so based on the first season, season 2 may cover volumes 3 + 4 leaving 5-12?

en.m.wikipedia.org/wiki/The_Apothecary_Diaries

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