Which song plays in episode 6 of Kenichi: The Mightiest Disciple at around the 21:40 mark? It's before the actual ending credits. It sounded a bit like the opening but changed up. But I don't think that's it.
I think that they used the instrumental song : Koike Joanna - Catch your dreams (Karaoke Version)
And they added the lyrics on a little part of that Karaoke Version, that they repeated.