Nighteye didn't like Deku, in fact he hated him for being Allmight's successor and not Mirio. But after the Shei Hakashi raid he is forced to take a DNA test for any relatives he might have to help him with a blood transfusion if ever needed. The results of the DNA test show that Deku is his and All Might's son. Now with Nighteye and All Might aware that Deku is their kid they have to figure out how to tell him. And if they can gain his full trust along the way. Along with secrets Deku's kept from everyone coming out what else could happen. ( no Sir Nighteye doesn't die he heals back to normal completely, and Mirio's quirk was temporarily erased meaning he gets his quirk back so everything after that is fanbased.)