a few things I've noticed about 4*s

• Misaki has only ever been paired with HaroHapi members (and the one set that she's alone in is a HaroHapi set, something that sets her apart from any other girl with this trait). my theory is that it's because if Michelle were to pair with any other girl or alone in a non-HaroHapi set, the universe would collapse in on itself. Michelle is HaroHapi
• speaking of that trait though: there are no girls who have only ever been 4*s in sets featuring only their respective band (not counting Initials & DreamFes) but the ones coming close with only one 4* in a mixed set are: Rimi, Tae, Tsugu, Misaki, and Yukina.
• meanwhile, Arisa is the only girl who has never been the 4* in a single band only set. rip
• currently the doubled up pairs, i.e. pairs we got twice, are the Udagawas, the Hikawas, Kasurimi, Evemaya, Kaomisa, Arilisa, and Tsugumoca. it's kind of funny to me that those would be repeated when Yukina has managed to pair with every girl in her band (and Ran) exactly once so far, but here we are
• the only vocalist who has yet to pair with another vocalist is Kokoro. everyone else has paired with one at least once (Kasumi-Ran, Kasumi-Aya, Yukina-Ran)
• the only girls that never got a (non-DreamFes/Initial) unpaired 4* are the Hikawas, the Udagawas, and ... Kasumi for some reason