imo Kokoro's voice shines the most in duets & unit songs (Romeo, Wacha Mocha, Kimi ga Inakucha, Hare Hare Yukai, the all-bands songs ...) and I?? love that so much???

Kokoro's happiest when everyone else is happy so she's gonna give it her all even more when she's singing with people who are having fun just like her ... I know it's probably just the voice contrast but this is how I wanna think about it, we don't deserve Kokoro ......