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人妻の唇は缶チューハイの味がして

Chapter 12.1 is generally categorized as an extra or "bonus" chapter. In this specific series:

For official English translations of major titles by the same creator.

These "point" chapters (like 12.1 or 12.5) often serve as short, atmospheric vignettes that flesh out the emotional state of the characters rather than advancing the main plot significantly.