you were the classic "nobody"

it didn't make a difference in anyone's life, no one cared to know who you were, etc., and because of that you developed a mental disorder that made you heavily emotionally dependent on anyone who paid attention to you

you ended up buying a vhs tape in a store and when you watched it you ended up summoning a ghost, Sunny Day Jack, and because you freed him he started to love you in a sick way

and you shared this unhealthy love

Jack was walking down the street looking for something to give you as a gift, entering an alley he saw that you were next to a bloody corpse

that person had flirted with you, and well, in your opinion it would ruin your relationship so you killed her

Jack was speechless for a while, but not out of shock, but pure joy and passion to see that you loved him this way

"my sunshine....."