Ritsu was born with the curse of the sign of the monkey.
As far back as he could remember, his parents always had to apologize for everything he did, so he is very unsure of himself. He feels that every day, he is robbing the world of its air by breathing.
He found that it always made him feel more comfortable to dress like a girl, but that only gave his parents even more to apologize for. Since he looks so much like a girl, that's what Tooru thought when she first saw him, until he accidentally transformed. Somehow, Tooru convinced him that he does have a reason to live, he just hasn't found it yet. Shigure likes to play with Ritsu's insecurities and gullibility, much as he does with his editor, Mitsuru. When the two meet, they realize they have this in common.
In the final chapter of the manga, Ritsu tells Kagura, while giving her one of his female kimonos, that he has asked Mitsuru on a date, and in a bonus story in the first fan-book, he and Mitsuru are a couple.
Natsuki Takaya derived his name from the eighth month, odakaritsuki or "rice harvest month," which is the month of the monkey, of the traditional Japanese calendar. In author's notes, Takaya said that she regretted how small of a role Ritsu played in the main story.