Based on the erotic doujin game by capture1.

Yuina is in love with her blood brother. One day, a mysterious voice leads her to a strange place. She is attacked by a man without knowing why, and she is in desperate need of help. But then, a ghostly succubus appears with a light and saves her! The succubus possesses Yuina's body and starts to attack her sexually. The mysterious succubus, who is not bothered by the flustered, naive Yuina, squeezes every man she can get her hands on. What will happen to Yuina in the world of succubus? I want to go home...... to my brother...... I wanted to "connect" with my beloved brother! I've been "connected" to a lecherous succubus! But this is just the way it is.......

(Source: Getchu, translated)