Toraware no Shoujo: Bluebird of Happiness (2019)

Ai is a young sickly girl that lives with her overprotective father. Many rooms in the house won’t open, and when her father Jugo is not around she’s locked in her room with just her "imaginary" friend Bosco for company. She believes that her father’s strict behavior is out of concern for her health, but one day she discovers something which changes her mind. During her quest to find the main door key she learns that she has very little time to leave before it’s too late…