Moon, however, made it clear that, in writing the series, he focused more on the relationship between the characters rather than on conveying his own message, believing that, in telling their stories in certain situations and with certain narratives, the message would naturally arise as by-product. The relationships between the main characters are of three types: Kang Yo-han and Jung Sun-ah's relationship is expressed by the key phrase "I want to have you", Kang Yo-han and Kim Ga-on's by "I want to know you", and Kim Ga-on and childhood friend Yoon Soo-hyun's by "I want to protect you", although these three wishes are sometimes one-sided. The relationship between Yo-han and Ga-on has been described as a "bromance" in which the two characters attract each other like magnets due to their differences. Speaking of how he wrote the characters, Moon stated: "When I created the characters, I completely ignored the genders. [...] Cha Kyung-hee is simply a powerful and ambitious figure, and Yoon Soo-hyun is just a detective who wants to protect her first love. They are both familiar characters who often appear as men in Korean dramas. In contrast, the role of Kim Ga-on is often given to female characters. Characters trapped in conventional gender roles are obvious and monotonous, and I think the prejudice that all women must be autonomous and men can be flat is also artificial. Every human being is an individual."
