I had this exact same unsurety. However, because Case 2.5 (the as-of-yet-untranslated Volume 1 bonus chapter) is titled “Premature Ejaculation Therapy”, I think it's the latter.
I had this exact same unsurety. However, because Case 2.5 (the as-of-yet-untranslated Volume 1 bonus chapter) is titled “Premature Ejaculation Therapy”, I think it's the latter.