There are moments in Black that you could view that way, but I think it's more that for Kyoko the family has already been ripped apart by Gorgom with the death of the elder Akizuki and Nobuhiko becoming Shadowmoon. Kyoko lost her father and her brother, she didn't want to also lose Kotaro as well even though she understood that he was Kamen Rider Black and Black was the only thing standing between humanity and Gorgom's new world order. Also to, she knew how much it broke Kotaro's heart to have to fight Shadowmoon because he was still having a difficult time accepting that the man who was Nobuhiko was basically gone. Kyoko and Kasumi had accepted it, Kotaro had not and Kyoko knew that would be his greatest weakness in the coming battle.
Out of Rider couples both official or implied that I like:
Godai and Sakurako-Never aggressively explicit in the show but I think it's evident enough to count. She cares pretty deeply for him, so much so she was even angry at him at first for putting his life at risk by taking on and using the power of Kuuga.
Takumi and Mari-These two had kind of that classic guy and girl who are easily annoyed with each other but then once they each get to know the real person they start having a connection.
Makoto and Ozawa- This one might be a stretch on my part but I always liked that Ozawa had such an unwavering belief that Makoto was the right man to be G3. I think this helped Makoto because she believed in him even when he didn't believe in himself.
Terui and Akiko-They have an odd-couple appeal that works in context. His relationship with her is kind of an ultimate indication that Terui has moved on from his anger for revenge after losing his family.*..and cue the Aki' haters*
Kazami and Junko- I think it was Igadevil who said something to the effect of this is the great untold love story of Kamen Rider and I agree actually. It seems very strongly implied in the early going of the series but it never really goes anywhere. This is something The Next would have been an opportunity to rectifiy but as usual Inoue was more concerned with his own pretentious horror movie about idol singers.
Tsukasa and Natsumi-(despite the friggin hot mess that is Decade). Natsumi is good at checking Tsukasas ego when it balloons to sekai size proportions. In some of the series better moments it creates an interesting dynamic IMO.