Board Thread:Questions and Answers/@comment-44754903-20200109133410/@comment-30418729-20200111135123

Since the new rival has already come to school, the game won't allow the last rival to date senpai, because this new girl has already met him, so senpai will devote more of his time to his new "friend", but still stay friends with the last. If we have any special cutscenes or events to show that the last rival doesn't want to try again with senpai will be entirely up to Yandere Dev.

It's better to talk about things like this in the official discord server, because you have a change to get an actual response from Yandere Dev