Yousuke is a college-aged student who became emotionally damaged in youth from seeing his birth mother repeatedly engage in adulterous acts while his father was away. Now, his father has decided to remarry. His lovely new wife, Misako, is moving with her daughter into the house Yousuke previously inhabited alone. Will he accept her as his mother, or use her to have his revenge on the mother who tormented him for so many years?
Gibo is a Japanese adult visual novel. The plot proceeds at its own pace, pausing occasionally to allow the player to intervene by making a decision, resulting in a story branch. There are over 40 such decisions, leading to 13 different endings, some "good" and others bad. The game contains Freudian imagery and graphic depictions of sex.