Well I'm not sure about that. Look, for example the fight between Gaara and Lee in Naruto. We have the development of Lee in that fight, everything, we saw that he did so much to be a "good" ninja. But he lost. It doesn't mean that he's bad but he lost.
It will be not illogical if Ryuho win against Yuna I think. But you're right, it would be a bit strange, especially if they develop her background in this fight. But well it's not the first fight where the characters with his background developed, lose anyway.
And like Kaioshin said, maybe Yuna will be defeated but they will give an "excuse" to her or something to say "it's not finish, she's not bad" or something like that.
Maybe Ryuho will be really in bad situation but will win very very hard. Ryuho is Shiryu'son, he was trained by him so he's a genius. It would be a bit strange too if he lost against Yuna (and water > wind
)
And I think that Ryuho will have a background too. I can't believe we will have nothing about Ryuho' story.
A draw or an interruption would please me
.
But I prefer to see Yuna' background during a fight against martians, major arc I think.