If I made a Moonie fangame, it would just be an Omori fangame that follows Moonie and Haru.
Haru returns to Faraway after her dad took her with the divorce, and she brought her best friend from the city, Moonie, with her, Haru is ready to take revenge on Sunny for forgetting about her.
She arrives literally one day after Sunny and his mom left Faraway, so her whole plan is already ruined, then you play as Haru, bossing Moonie around, talking with NPCs and making up plans to mess with Kel, Hero, Aubrey and Basil, who are still very deeply affected by the true ending of Omori, but Haru doesn't cares because she's a little gremlin and Moonie is her dumb minion, like yzma and kronk.