I post art

Basically Nightmare has a lvl rush that midway through it his body went passive while his corrupted half went on a frenzy attacking people left and right. While doing this, and having to deal with both Ink/Dream attacking him and lost in panic, he accidently stumbles on a UT variant where Asgore could witness Dream deciding to actually shoot at a passive Nightmare. But before Dream could actually do it, Asgore runs in and hugs Nightmare and attempts to passify Nightmare from what he assumes is a Magic break, or rather a thing he's seen from the war (ie I like to think that monster children require to have a parent bond of sorts because if a monster child is deemed unloved and unable to receive any support, they often then to autodestruct. As their magic left unused and monitored could build up and eventually be too much on the body.) Naturally Asgore succeeds in calming down Nightmare , and then instantly proceeds to yell at both Ink and Dream and any potential involvers and shame them for attacking a child monster in need. And proceeds to refuse to listen to any of them or their excuses. Deciding its the best option to keep Nightmare in his care, Meanwhile at first Nightmare just blanked at this whole situation. He's mentally exhausted after all of that, so he kinda just does whatever his child like mind wants to do. Ie now Asgore and Nm have a child/parent relationship to a degree. Naturally Nightmare decides to reveal it all to Asgore later on when he needs to get back to work and kinda looks up to Asgore for helping him when no one else would. For Nightmare its the one of the few times he's been actually allowed to feel like a normal child. While being flustered Nightmare could ask Asgore if its alright for him to come back during his free time. I like to think this asgore would agree to it, that Nightmare would have a place to come and rest with him. and whatnot >>