Antonio Gargazulio Duarte/Bong Bong
Bong Bong is his nickname. He's the protagonist of the story. Born in Manila, he finds himself utterly lost in the culture-shock of coming to San Francisco. Bong Bong does not practice the mental discipline necessary to combat his frequent paranoia, so he gradually drifts into a state of insanity. He's accused of being schizophrenic but is never diagnosed. He enjoys cooking school, reading, and looking at the heavens through his telescope.
Frisquito
Frisquito is Bong Bong's best friend from back home. He's a painter and a bit of a narcissist. When Bong Bong leaves, he promises to write often. For a while Frisquito responds, but eventually he loses interest in his friend, no longer feeling the connection he once did. By the end of the book, he is left a silent ghost to whom Bong Bong desperately writes.
Carmen
Carmen is Bong Bong's sister. She owns a home in San Francisco with her husband. Bong Bong comes to live with her at the bidding of his parents. Even when they were young, the two didn't get along. Now she's convinced that he's gay, and she's anything but accepting of it. She longs to be a fashion model and worries about her reputation. Eventually she gets fed up with Bong Bong and tells him to move out so she and Pochoy can prepare for their new baby.
Pochoy
Carmen's husband is a reserved man. He's a computer programmer. In his home, he mostly listens to his wife at the sacrifice of his personal desire.
Charmaine
Charmaine becomes Bong Bong's girlfriend. She flirts with him first, setting the general tone for their relationship. When Bong Bong is kicked out by Carmen, he moves in with Charmaine. At this point, they still haven't had sex -- despite trying. She cares about him, but she soon loses hope in him as his sanity starts to drift. Eventually she comes to believe that he is a schizophrenic, and she fears him. The morning after they first have sex she packs up and leaves him.