I actually thought the animation for Kasen vs. Sonic was good. I know a lot of people had problems with it, but I thought it was great.

Even if you disagree about Sonic losing, given the power gap between the two it makes sense for Kasen to take little damage. It also put Kasen in some kind of a mentor or elder role to Sonic, and let Kasen show how far she had come by defeating someone who had been down the same path as her. She wasn't just fighting Sonic, she was TEACHING Sonic. And I think that's very heartwarming in a way. That Kasen would take the lessons she learned and help someone who was just like her.

If this weren't a Death Battle I'm sure they would have ended cordially and taught each other well. The alternate ending is weird, even if heartwarming in its own way. It was nice to see Kasen reunite with the other oni, but it feels weird to have her just stand there and take that punch.

I haven't read Sonic's comic though (but after watching this fight I think I might read a synopsis!) so I might be missing stuff but as a big Touhou fan I thought they did Kasen justice and from what I saw they treated Sonic with the utmost respect. What character has ever gotten an alternate ending made just for them?