Hello!
There are 5 main Love Interests who will get the most development and scenes:
Elena, Anna, Katy, Micaela, and Julia.
Then, there are the secondary Love Interests who will also have complete relationship paths with different endings, but a slightly smaller number of scenes:
Susan, Fleur, Brianna, and Sylvia.
Next, we have the side girls who will have a notable presence and an ending, but won't have as much content as the rest:
Lara, Denise, Mirai, (?).
Girls like Clarissa are in the story either to give more variety to players who like to sleep around or to play a small part in the overall narrative (not always positive).
That being said, this categorization is rather arbitrary since if some girls turn out to be incredibly popular, I'll find a way to provide more scenes for them (as long as they feel natural), and if some are generally disliked, their role may be reduced to primarily plot-relevant scenes.