Because the anime only covered this early part, their relationship isn't properly developed, and not even explained. There are still many aspects of the story that aren't presented, which make all the writing seem shallow within the context of the anime. For somebody that hasn't read the manga, this would easily come off as a low quality story, with a very low quality and hard to understand dynamic between the characters.
I've watched every yuri anime you can imagine, and plenty of manga, and citrus is my favorite manga, especially citrus+, however, I can't give the anime more than a 6/10. It's really a shame to see. It makes me sad to say I like citrus, and have people instantly think of the anime, which was notably worse. The anime kind of feels like a short demo or promotion for the manga. A trailer. Very shallow, quite short, lacking emotional scenes, atmosphere, events. Season 2 won't be coming out either which is a shame, and also surprising seeing as it's one of the most popular anime of its genre.
