You create a character and give him a very detailed personality, you know his parents, how the character grew up,
where he works, where he lives right now, what he likes to eat, drink and watch on the tv, music, favorite snack, love life,
hobbies. Everything you can imagine.
Let´s the name same Adam & Eve
Maybe that character lives together with a partner, do the same for the partner.
There are unlimited ideas that you can create just with this situation.
Give them extreme character traits.
Adam is super jealous and insecure.
A new neighbour (Paul) moves into the apartment same floor.
From that point it can develop in unlimited branches.
Adam can start stalking Paul and finds out a dark secret.
Adam can start stalking Paul and kills him in an accident
and has to hide his body.
or
Eve meets Paul and he starts stalking her and then
he kills Eve or Eve kills him or Adam and Paul kill Paul.
or
Eve meets Paul finds him very cute but Paul falls in love
with Adam, Eve kills them both
and so on.
You can make up plenty of ideas and it will get easier the better you
know your characters. Eve can be choleric and violent. Paul is homosexual. Adam
is insecure or Paul is inscecure, Adam & Eve are both violent