Okay, I forgot to put in Butch in the beginning so he's at the end.
Here's reasonings for the characters.
Ash: "HI MY NAME IS ASH KETCHUM AND I WANT TO BECOME A POKEMON MASTER. HI. MY NAME IS ASH KETCHUM AND I WANT TO BECOME A POKEMON MASTER. He rarely talks about anything else so you try finding another theme song for him! lol
Haru: This one actually had some meaning behind it. When Haru was little he was confused about the zodiac and went to go ask Yuki about it and this song just reminded me of them.
Seto Kaiba: Despite the peppiness of this song it pretty much describes him in a nutshell.
James: I chose this song to reflect upon James and Jessie's friendship or relationship however you would like to see it.
Italy: I know this is a TOTAL cop-out but I had NO idea what to give him and sorry if it's the wrong Italy. :/
Sakura: So this song was MEANT to feel like it was her "destiny" with the cards and how she was attached to them but then it kinda ended up seeming like a TomoyoxSakura thing, but take it however you want.
Luke fon Fabre: So, I picked this song because he's changing throughout time in the game and there was just so many pictures of Luke and Asch that I just couldn't resist.