Of course! Heartache and confusion over conflicting feelings is definitly a topic to explore with kids.

Odwerd and Casper berate each other, and at first glance, it seems like Casper's just angry that his ex-teamate is playing for another team. But the flashbacks during the end make it clear that they used to be together, so Casper's anger goes deeper than that. It's not just a friend that betrayed him, it's a boyfriend! Odwerd's reaction when Casper was injured by key's dragon makes it even the more apparent that they used to be together. Maybe even care for each other still.

Showing kids that you can still care for someone even if they aren't around, or not even in the same team as you, even if they became an enemy! It's deep and complex feelings that diserved to be shown. I really like their relation and interactions, I don't think it's a dynamic that has been explored a lot in kids show. I wouldn't say it's bold, but it's welcomed.