Ah, regarding Wada Fes.
It was announced this week on her official site, that Kuu is going to collab with Masayuki Suzuki, the singer of Rats & Star, the original artist of Megumi no Hito.
They don't mention what they gonna sing, but I guess it's clear.
https://rhythmzone.net/koda/news/detail.php?id=1065453