She loves this other guy, but she spends time with the male lead and falls in love with him. The other guy who she loved does pursue her too.

I can think of a couple where the other guy doesn't pursue, at the least. In the manga Kyoushoku Soukou Guyver the main character fights desperately to protect his childhood friend and crush, despite the fact that she only has eyes for the student council president. Doesn't fit perfectly since the SCP isn't really interested in her, aside from the possibility of using her to get to the hero as the hero's newfound powers could be useful in defeating his enemies.

Also, in the manga Uwagaki you have once again a girl who loves someone who doesn't really love her back. The story starts out with an argument as she tells the boy, who has yet to confess, to give up on her. Their mad scientist teacher hears the argument and that the girl already has a boyfriend, and as an experiment splits her into two bodies, erasing all memories of or related to the boyfriend from one. The hero's task is then to make the copy fall in love with him more than the original loves her boyfriend, and when the two are finally fused back together whichever love is stronger will erase memories of the other love. The very first chapter then ends with the boyfriend asking to break up (it's later revealed that he'd kind of been stringing her along while really he'd been in love with someone else for years).

Higanjima has the major female character (not really a female lead though, she doesn't have much screen time) in a relationship with someone else at the start, but later fall for the MC. (I haven't finished the sequel series so I don't know whether this will turn into a relationship)

[url=]https://www.mangaupdates.com/series.html?id=6819[url] Kirarin Revolution

Ranma 1/2 kind of fits the bill. Female Lead does love someone who's not the Male Lead, but that someone doesn't love the Female Lead, never pursues her at all, actually.

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