Imasu's family was both indígena and Spanish; according to Magnus, "more mingled even than most mestizos."
At one point, Imasu was inspired to take up music because his sister loved to dance.
Imasu met Magnus one evening at the Plaza Republicana in Puno. He was playing the charango. Both were immediately attracted to each other, and Magnus asked him if he could teach Magnus. Imasu, wanting to spend time with Magnus, agreed to teach him.
His lessons never taught Magnus enough, who played horribly enough that Imasu was approached by dignitaries of the town to beg him to stop Magnus. Though he initially encouraged Magnus, he eventually admitted that Magnus was awful and hopeless to teach music to. Magnus then agreed to give up on music, but Imasu and Magnus only grew closer.
With their budding relationship, Magnus, with his friends Ragnor and Catarina, decided to stay in Puno longer to be with him, though it was not specified how long their relationship lasted. Magnus was the second person he ever fell in love with.
During the span of their relationship, Magnus never got around to telling Imasu about magic and his demonic origin; though Magnus wanted to tell him everything about his past but, wanting to be careful and afraid of getting hurt, did not. Magnus had even considered offering that he and Imasu live together, before Imasu broke up with him. Imasu felt that Magnus was too ephemeral. At this, Magnus laughed and told him that he was "the most permanent person" he would ever meet. They never spoke to each other again after that.
Imasu was said to be gorgeous and incredibly handsome. He had brown skin, sparkling dark eyes and normally rumpled hair.
- What Really Happened in Peru (first and only appearance)