The Anchorite (1976)

Eleven years ago Fernando Tobajas, a man of a certain age, decided to live in the bathroom, in which he created a small apartment, and never leaves it. Tobajas has given up everything except vanity, and his contacts with the world are reduced to visits from friends and messages sent through the toilet inside aspirin tubes in the hope that someone will receive them and know about his existence. Arabel Lee, a beautiful girl, finds one of those messages.