Dude, you should do more research on abilities, Escanor's grace Sunshine let's him harness energy from sun not day. The reason Escanor becomes weak at night because Sunshine is the ability of Mael a goddess clan member and Escanor's mortal body cannot handle it. At night Sunshine user is at his weakest form means he has no buff from the ability and is at his base power. MC in your fic is not a mortal human but Asgardian, at night his strength should be what a normal Asgardian would have(if he never trained in his life to get stronger and only relies on his sunshine ability, which in my opinion is pathetic).
Other than this diffence in opinion with MC's ability. This fic is great👍.
