^ It's confirmed that Mikaeri is the 9/10/11gen song
Here's a translation of Sayu's interview from the Natalie.mu article
"About her last single
This time it’s a triple A-side single! “TIKI BUN” is incredibly cool. You could say it feels like the current Morning Musume, but I’m really happy that Tsunku♂san gave me such a cool song for my last single. Also, “Shabadabadoo~” is somewhat my solo song!
In my past 11 years, my solo parts in singles were nearly nonexistent. And yet, singing all of the solo lines in my final single is something like a miracle! [or getting a solo song in her final single is a miracle?]
I’m excluded from “Mikaeri Bijin” which is sung by the other 9 members, but all 3 songs are really different from each other, so please look forward to them!
Less than 100 days until her graduation concert
I’ve been with the group for over 4000 days, so it’s very strange to think that I’m within my last 100 days. But I’m of course very glad that my last day will be at Yokohama Arena, and I think that anything I can do with the current members is meaningful, so I’m awfully happy. Everyone please come and support us!"
Source: haro-puro.tumblr.com