My story idea is NEET living by her own thanks to financial support from parents is only checked on by her younger stepsister, who is like 14. Stepsister one day tells NEET that their parents want her to move back home after her lease is up cuz they don't want to keep paying rent on her apartment. During the ensuing bout of depression, stepsister tries to comfort NEET, and NEET kisses her. Stepsister accepts her sister's feelings and reciprocates and they decide to do what they can together before NEET moves back home, since it'll be harder to hide the relationship. So they go on a couple dates and have a really good time. One day, as the deadline draws near, NEET sleeps with her stepsister. A few days later, stepsister gets sat down by her parents and her parents tell her that NEET committed suicide. NEET left a note for her apologizing for the relationship and for sleeping with her, saying she knows it makes her a horrible person, even if stepsister doesn't see her that way yet. Thanks stepsister for making the last bit of her life a little happier.
The end is grown up stepsister leaving flowers at NEETs grave, thinking about how she knows NEET wasn't a good person, but she loved her anyway and still misses her.