So I recently came across the game scripts and learned something interesting. Apparently, the event tied to the parent image involves Alesia going to the beach with the protagonist wearing a thin (possibly see-through) bikini that matches her skin color. The protagonist is flustered by this, but Alesia tries to assure him it's normal in her home country and he'll get used to it soon.

Considering the above and the existence of this topless version in the game files, I think it's likely there was an earlier draft of the event in which Alesia explains that she would swim topless in public in her home country.