Izumi and Ryouma meet as children whilst on set of the Happy Wedding commercial. Ryouma falls in love with Izumi, whom he is convinced is a girl, and spends the next 10 years thinking about "her". When they meet again, they are on set for a part 2 of the Happy Wedding commercial. During this time, Ryouma discovers that the girl he has been in love with for the past 10 years is actually male. Ryouma storms off, leaving Izumi and Shougo behind as they exchange comments about Ryouma's personality. Later, Ryouma heads to the Sena household, still in disbelief that Izumi is actually a boy. He wants to see Izumi again in an attempt to get rid of his feelings once and for all. However, it doesn't go as planned. When Izumi returns, Ryouma just finds himself attracted to him. The two struggle for a little bit as Ryouma chases Izumi around, demanding that he strip so Ryouma can really see that he's a boy. Shougo arrives and stops Ryouma. After that, things are awkward between Izumi and Ryouma. Izumi is upset over the whole experience, both because of how forceful Ryouma was and because he's concerned that he actually liked being touched by Ryouma. Meanwhile, Ryouma forces himself to come to terms with the fact that, regardless of gender, he is still very much in love with Izumi. He apologizes to Izumi and confesses his love to him, and the two begin their new relationship as "texting buddies". This continues until Ryouma compliments Izumi's manga and offers to help him finish it before the competition deadline. Their friendship begins there.
They remain friends for a short while, but it is obvious that they become closer and closer as the time goes on. Izumi finds himself falling for Ryouma, and after suddenly being hit with that realisation, he runs to Ryouma's apartment and kisses him. Izumi tells Ryouma that he wants to have sex with him, which, after a bit of convincing, Ryouma agrees to. The next morning, Izumi appears to be in a lot of pain. Ryouma, who looks guilty, asks why Izumi even came to him last night, and if he was just upset by something and ran to Ryouma for comfort. Izumi quickly declines, sitting up and regretting it immediately when he remembers the pain he's in. A moment later, he recovers and realises he never told Ryouma the reason he came. He tells Ryouma that he loves him, which results in Ryouma crying and returning the declaration of love. That marks the beginning of their relationship.
Their first date is at a theme park. Izumi secretly asks Rei and Shougo to come, as he is afraid of being alone with Ryouma after the painful sex they had before. Despite being excited for his first official date with Izumi, Ryouma finds that he's forced to spend more time with Shougo. The date continues for a while, before Ryouma manages to lose Shougo, and while Rei is away getting snacks, Ryouma takes his chance and runs away with Izumi. However, Izumi stops. He is hesitant to leave with Ryouma because he's knows Ryouma will "try something dirty". He admits that it was extremely painful when they had sex for the first time, which causes an embarrassed Ryouma's mood to deflate as he leaves. That's not the end however, as Ryouma goes home to study gay sex and the appropriate preparations for it. Meanwhile, Izumi and Rei have a conversation about it, in which Rei suggests that Izumi tops, so that way he won't feel pain. Izumi likes that idea, and heads over to Ryouma's apartment to apologize. They both end up apologizing in sync, which causes them to laugh and share a kiss. Despite Izumi being dead set on topping, Ryouma insists that he's studied enough so that it won't hurt this time. Reluctantly, Izumi agrees to bottom and they have sex for the second time. Afterwards, Izumi appears to be feeling blissful and very content, and praises Ryouma for being so good. Ryouma is relieved that Izumi enjoyed it, and Izumi pecks Ryouma on the lips and asks if he wants to go for another round. That marks the beginning of their sex life.
They continue steadily for a while, their only obstacle being when Ryouma was hypnotized by a director and briefly forgets Izumi. His memory comes back to him when he is smacked on the head by Shougo, who then claims it was intentional. After that, the two continue dating happily.
During a drive home, Ryouma asks Izumi to move in with him. This takes Izumi by surprise, and asks if he means as roommates. Ryouma says no, and explains that he would like to live together as a married couple. Izumi is concerned about how Rei and Shougo will react, but Ryouma simply tells him not to worry and that he can think about it. Shortly after, Rei discovers that Izumi's stalker has discovered where Izumi lives, and begs Ryouma to let Izumi stay at his apartment for a while. Both Ryouma and Izumi are excited by this, since they'll be getting a taste of what married life will be like. In all the current chapters, it appears that the two of them are enjoying living together.
The two appear to be becoming more open about their relationship. After being caught kissing by Kuroi, Izumi tells him that he and Ryouma are dating. He goes into detail, telling Kuroi about how in love he and Ryouma are, and even urges Kuroi to ask questions, which results in Izumi telling Kuroi all about their first kiss and how much sex they have. Shortly after, Ryouma tells his boss that he and Izumi are in a serious relationship.
After a time skip in the manga, Izumi and Ryouma officially got married.