Yep, all forgor.
And yes, the one that was thought to be a rival for Chitoge's affections was actually secretly a new (passive) player for Raku's heart. It's pretty obvious Seishirou likes him, but refuses to admit it to herself or anyone else for that matter. She has no designs on being romantic with Chitoge, she's just a sworn protector of her. In fact, it's because of her loyalty that she will be reluctant to act on her budding feelings for Raku, even if she does realize what they are. Why would her sworn protector try to steal away her lady's boyfriend? That would be such a horrid betrayal.
Anyway, there's at least one more 'serious' contender that was introduced in the anime, and I actually despise her- worst girl in the story, in my opinion... Maybe two if one wants to count Kosaki's own little sister who seems to not realize she forms a crush on Raku after he saves her from some rough guys while she passes out on her way to her first day at high school, so she never could recognize who he was, but he also lost his pendant in the same moment, so, uh... yeah. She ends up keeping his pendant for awhile because she thinks it belongs to her 'prince charming', and refuses to admit it is Raku's, believing he's a horrible person manipulating her sister and that he's trying to add her to his 'harem', too, and nothing like her pure 'prince'.