⏳| When Nova first transformed into a mortal, she faced her first problem: hair. Usually her hair can float in the air, a side-effect of her time powers.
As a joke, no one tells her about braids and ponytails. Think of it as a revenge for the pranks she pulled on them.

⏳| Because pure-gold visors are too suspicious in the mortal realm, they were transformed into normal yellow glasses. But she still kept her golden watch. Both items still work for her.

⏳| It annoyed her beyond that she couldn't summon any drinks she wanted. Not only that, she didn't know about being hungry and sleepy is. It happened on her first night being a mortal; she passed out from not eating and sleeping. Nova legit thought she was dying—

⏳| Nova and her friends will be humans, attending a school where Humans, Angels, Demons, and Monsters attend. And all of them are actually pretty hot in mortal form. This school also teaches magic, but they all will only have WAY WEAKER versions of their powers when their mortals. Such as Nova being able to slow time that it'll look like to others that she's moving fast. 

⏳| Nova snuck a very important mirror from her Onyx Castle. It showed her any point of time anywhere with anyone, but only from the past. She infused many items with certain abilities, even areas around the world that it just became a hobby. Another one is a Golden Goblet that'll never run empty of Beer. Then there's that Waterfall but that's for another time.

⏳| First week in the Mortal Realm, and she was immediately bored. She questioned why mortals spend their time on many useless stuff like 'dancing' and 'videogames' and things such as that. Don't they know that their lives are so short???

⏳| The choice of clothes were given to her by her mother and father since her choice of clothing is rather poorly, ESPECIALLY for a school with a certain dress code...
Okay that's a lie since her mother Toriel runs the school—

Okay so big time reveal about this AU. This City of the Four Races has secret parts and areas where mystical creatures and even GODS AND GODDESSES go for vacation or free time.
Examples:
Grillby, God of Hearth & Crops, owns a bar/restaurant that is literally based off his religion.
Sans, God of Death, works at a hotdog stand.
Asgore, the Sky God and King of the God Realm, works as a gardener. A GARDENER.

It'll be quite a shock to the kiddos to see them around.