Yuumi Kasai is senior by 1 year
Group Generation
Tsubaki Factory Generation 2 and Morning Musume. Generation 16
The groups are different.
Audition Cohort
No shared audition is confirmed in the published information currently recorded.
An unrecorded audition history is not treated as proof that the two are from different cohorts.
Trainee Generation
Yuumi Kasai and Rio Sakurai has no trainee history, so this axis cannot be evaluated.
Debut Year
2021 and 2022: 1 year apart
Yuumi Kasai is senior.