Responses
I wouldn't really say he's overpowered. You can clearly see even in the recent chapters that he has limits and it's not even crazy high; And plus the MC is not like the usual "overpowered genius MC" he's not all 'nonchalant, tall, handsome, and dark black hair' ykwim
Not bad at all, but kind of... boring?
Sure, there is a goal to read the letter and know more about friends that had to live on without him. It's all, however, trampled on with "overpowered genius MC" (TM) doing "overpowered genius MC" (TM) things. Unfortunately for me, not something to my preference.