I think the story changed the moment Dana reincarnated. When Aru remembered the death of his friends, he too was falling off a cliff to save or to soften Dana's fall. He was traumatized and felt guilty for what happened to them in the future and suddenly begins to insert himself more so than in the past with Dana because he had already fallen in love with her. If the story has changed, then it is possible that Aru's feelings had altered compared to the original story before he came back to the past. This would be caused by Dana because she is also reincarnated and will ultimately change some of the original plot. Sadly, I have a feeling that the FL won't realize or consider this just like the other romance manhwas with reincarnation.
Judging by the way Aru talks to Stella in chapter two. He looks at her in slight distaste? Why is that? Because according to Dana supposedly Aru and Stella live happily ever after. When Aru defeats Edgar. Here's my theory I think there must have been a betrayal or something. But also can we truly rely on Dana's memory alone? In the first chapter we see Aru complaining to Dana about Stella but how can we be so sure he was actually in love with Stella? Idk I just felt it was so abrupted when she said "go confess to Stella" what? That's so random. Did he truly love Stella?