holyyy so the ML can feel the MC he is facing is not the original MC

MC is the OG MC its just that the current MC had TL memories and modern memories but undoubtly he is the OG MC, he got reborn as a baby there, because in the first few chapters he has no idea where he is I just assumed he got reborn with his past life memories somewhere random

I think the reason ML said MC doesn't have the sunny bright personalities he once have well perhaps because MC already experience a lot of harsh things in life not to mention he got killed by ML he once adored and then got reincarnated again, same for ML he also changed, his no longer the child that likes sweet donuts without ulterior motives

Pretty much this.