Didn't expect a duo like Kana/Yayoi to get a song like that. Huh...
As for LTD04, Ritsuko/Karen and Tomoka/Iku are weird duos and you should feel weird.
Also, I assume Miki REALLY didn't want a duet with Tsubasa so she forced Hibiki unto her. Or at least, that's what my headcanon says. :p