'The day I decided to be Nina' is a documentary series in nine episodes about children making stout-hearted decisions that have an impact on the rest of their lives. Guido is an 11-year-old boy who is often mistaken for a girl. That's not really bad, because Guido likes to wear a ponytail, is crazy about horses, and football is a nuisance to him. As a matter of fact, Guido would rather just be a girl!