Karl is a parasitic worm who spent a lot of time looking for his ideal habitat. He finally found it in a corner of the intestines where he can survive undisturbed... at least until today. Brian is a white blood cell. It is his first day of work. A faithful servant of the body, but also a curious creature with a generous heart, he is supervised and directed by the omnipotent brain, manifesting itself as a telephone. In a world threatened by the problem of coexistence and compliance, is it still possible to be 'Gut Buddies'?