I think he did harbor affection for Lizzy in the past but was always suspicious of her kindness so he pushed her away. Once she dies however he felt intense regret that why he risked everything to turn back time so he could do everything right
Actually rather than leon being mentally 30 i think hes mentally 10 with his past memories... theres often times hes acting like a child (skipping practice, clumsy, etc). So i think both are changed with every actions like ur personality is affected by environment
Okokok this makes sense since there was a panel where he started questioning did the past he came from really happened, as if he has started to forget the time he came from little by little.
This made me rise few questions, leon is 10 physically and 30 mentally right and he didn't care for lizze before but now he is a child who is 30 yera old mentally is likely lizze. I mean a child will looks like a child only to everyone even if theybare in a 10 year old body... so this seems kinda sus to me ┑(￣Д ￣)┍