I'm not surprised it's not doing better in the charts:
- the song is boring - pretty maybe, but boring
- it's not enough to have pretty covers
- the fans of soloists wouldn't necessarily buy this cuz they're used to seeing their favourite as solo act, at least that's how I feel. I didn't buy this single
- the kids don't know it's Kirari singing in this song lol
- Japan couldn't care less about H!P being 10 years old
I didn't expect this song to do extremely well in charts, these random groups haven't been doing well anyway (NUN, DEF DIVA etc. Def Diva was maybe oricon weekly #1, but they were the new least selling #1). Making these units seems to be just fanservice, it's not really a good way to try to reach a larger audience.