Both of them only had have sex with women until now... They were heterosexual and this is the first time they've fallen in love with a man... But they haven't fully realized their feelings nor talked about it... So we don't know who is "seme" or "uke", and they don't know either. Your sexual preferences like that is something you can only decide after you have the experience.
The dark haired one, I get their names messed up, is pretty comfortable with his sexuality. He's comfortable with both men and women, but the Blonde one is much more apprehensive about being intimate with a man, though as we can see he is gradually warming up to the idea. That's a big leap to make, in his defense. I mean it's obvious they're attracted to one another, but as the Anony above said, they don't know what they are either. This story is a learning process for both of them.
...are they versatile?
I. am. confused.┗( T﹏T )┛