Haré tends to think about things too much, and Guu takes advantage of that by psychoanalyzing Haré at every opportunity, and playfully taking advantage of Haré's neurosis. Hare is also seen reading the Hare+Guu manga. At the end of the manga, six years after Guu suddenly disappeared, Hare has become a teacher at the village school and marries Marie, who gives birth to his daughter. Upon seeing his face, the child gives him Guu's trademark smirk, which comically alarms Hare and prompts him to name her "Guu". In the omake, it appears the baby also has Guu's snarky attitude and generally demeaning behavior towards Hare, and she likes to act spoiled to annoy Hare.
Source from Wikipeida