I think I read somewhere that Luca thought his uncle didn't really love him and did it out of responsibility and since his aunt changed he decided to keep her close. I think he wants to be happy in this timeline, not sure tho. https://forum.novelupdates.com/threads/i-will-make-an-effort-to-change-the-genre.110458/
I don't know how to use that "This topic may contain spoiler" so this is the warning
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From what I've read from the spoilers in the comments, I believe Luca is being like that with his aunt because in his past life, she saved him and was the only family member of his that he could truly rely on. And, he doesn't want her to have a relationship with the uncle because the uncle told him that he saved him because of his duty, and not because he loved him and they were family. So I believe he isn't really being that clingy, but stopping the uncle from being so (like the stuff with the hand). Even though he is an adult on the inside, I think he can still love his aunt as family like the people that besides being adults, are still "clingy" with their parents. And I still don't think he is being that clingy xD Maybe he's giving off that vibe because he's always interfering with the relationship between the aunt and the uncle. And I think the uncle is being "flirty" with her maybe because he fell in love with her at first sight? I don't really know.
(This was information that I took from the comments so it may not be 100% right)
I think I read that he wanted someone or him and his family to be happy maybe ?? so he wished he could turn back time so they didn't die. But you can read spoilers here
https://forum.novelupdates.com/threads/i-will-make-an-effort-to-change-the-genre.110458/
You can only use the tag on the original post. Which I did so noone can complain. It makes sense if his uncle said it was out of duty or he misunderstood because of the uncle's personality. The way the MC is portraying it it seemed like the uncle cared for Luca but we don't know what POV the book is in so there could be inconsistencies if it is 3rd person and not Luca's POV. I mean we say clingy but it's more of a he forgave her real quick. Also did she save him in the OG story? Because that doesn't sound like something the OG aunt would do. Still not quite sure why he is cockblocking his uncle though. Or why his uncle is so interested in his aunt
She saved him but they didn't put it in the novel so she could remain the villain, so the story isn't well portrayed, mainly the relationship between them. He's blocking his uncle because of what he said before he turned back time, so he doesn't believe that the uncle really wants a family and maybe he thinks that he isn't good enough or won't be good to his aunt?? And her personality is great, and she's also pretty so it's not that hard to understand why the uncle is interested.
And thank you, for the information about the spoiler thing :)
Spoiler:
Luca is a returner. He became attached to his aunt because she changed and protected Luca before she died in the original story.
the aunt is actually a returner too. Luca wished for her to be happy so she reincarnated in the modern world then read about the novel, then died and returned to being Luca's aunt with her memories from modern world intact. Luca became like that to his uncle because his uncle told him he didn't really love him before he died in the original story. But he only said that so that Luca won't get caught by the assassins.
Okay so just read some spoilers Uncle is also a returner so 3/3 people on the train have future knowledge he likes the aunt because in the OG timelines he hated her at first but at the end he kinda liked her and thought them meeting in hell wouldn't be so bad? This story is a maze. Also the family tree will get weird.
So, I have many questions. Luca is dropping too many hint he is definitely a returner.
Why is he being so clingy/jelly with the aunt? If he were a proper child it would make sense but he is an adult.
Why is he giving the uncle so much sass when they had a good relationship before?
Why is the uncle flirting with his aunt constantly? Is it not on purpose? Because he seems like he is into it which is not supposed to be his personality. 3/3 people on this train are not acting according to their book personalities and we only have reasons for 2 of them.