i kind a agree with you but i think he overthinking like us...
Actually not really, as overthinker use to think more when the communication is not exist in the first place, but in this story ml state to MC very clearly, so this is not about just being overthink it heavily lack of security and not many people like this,,
For example u overthink your loundry haven't been picked, but at the same time the people at home said 'it already picked' u would believe them and there no further thoughts about the same problem,
But people who have lower security about trust and comfort would overthinking about the situation and not only doesn't believe the people at home really pick the loundry but they also think badly "what if they didn't get it and the loundry get wet again by rain" "should I go back instead" etc etc ,
I approved of this explanation (*｀▽´*)
Hehehe appreciate it ε=ε=(ノ≧∇≦)ノ
MC is good at manipulate himself to the bad thoughts lol, even when ml already said that he wanted to be with him only and for his entire life, MC still thinking that he a substitute for a better candidate,
ig it the represents how bad lack of security MC has ,