Having graduated in audio-visual communication design and research from the Complutense University of Madrid, he created Walkie Talkie Films, together with Xiana do Teixeiro, in 2008. Whether as a team or on their own, Fonseca and Do Teixeiro have reflected on the relationship between what is and what is not human, the idea of nature and eco-social conflicts such as Queimar o Monte (2013), Sotobosque (2016), Somos Plaga (2017) and Soy Muro (2018) and the documentary comic Verde Invisible (2016). 

Fonseca is also the illustrator and author of the graphic novel (Fóra de mapa (2017) which received the 11th Banda Deseñada Castelao de la Diputació d’A Coruña Award).