This is yaoi, slice of life, will be mature, and certainly has a lot of controversial themes. If you have prejudice towards trans people, cross dressers, drag queens, or basically anyone in the LGBT community, this isn't for you~
Our characters used to be friends in high school. Your character was the goth kid that was in a fight every week. He smoked tons of pot, failed most of his classes, and was generally a cool dude to his friends. My character was the "fairy faggot" that was beat up twice a week. He wore feminine clothing, was amazingly smart, but had no friends because of who he was. Your character used to defend him and stand up for him, so they became very close.
High school ended and they fell out of contact. Your character's life for the next ten years is up to you. He can have gotten married, gone through college, gotten a good job, ended up homeless, made it small as a rock star, etc. From time to time, he thinks of my character, and he has convinced himself that my character probably became a woman, since he was always so feminine.
Their high school reunion comes around and he gets a letter from my character, asking him to be there. He doesn't reply, but he does show up. When he sees my character, he is wearing a dress, elegantly done make up, and looks absolutely stunning. -Insert your character's feelings about being right-
Just as the two of them start talking, my character gets a call and says he has to leave, but asks your character to meet him for lunch tomorrow. For whatever reason, your character says yes.
The next day, he is waiting at the agreed restaurant when a man walks up. He is shocked when he realizes it is his friend. Patiently, my character explains that he is gender queer and switches back and forth depending on the day. This makes your character uncomfortable, but as the two spend time together, their old friendship is rekindled and they find themselves drawn towards something more, though both resist for the sake of the past.
This can lead to romance or just stick with friendship. I just want to write a story of self acceptance and love that looks past societies norms and becomes something special and unique.