Much like civil war or the outbreak of some hideous disease, fornication in The Witcher is a complex phenomena which can happen suddenly and without warning or, alternatively, as the more predictable culmination of a long process of rising tension. From a narrative standpoint, it's sometimes presented in a reasonably convincing manner (both the Shani relationship in this video and a few of the one-night stands are pretty plausible), but more often than not the constant screwing around comes across as inexplicable and rather gratuitous. It also has a "gamey" element to it, in that there's a very strong urge to, so to speak, "catch 'em all"...which of course only further undermines the psychological realism and personal integrity (such as it is) of the main character.