I have some good news.
In case some of you wouldn't know about the ranks in C-mode and how necessary they really are to record your times, I am making this post for your information.
There are ranks, of course.
Rank is for challenge mode and how far you got in it.
Here they are:
Ra GOU - completed C1
Gi GOU - completed C2
Bu GOU - completed C3
Ra ZAN - completed C4
Gi ZAN - completed C5
Bu ZAN - completed C6
Ra EI - completed C7
Gi EI - completed C8
Bu EI - completed C9
For some time me and other people (mostly because of me xD) have been thinking that:
1) You must be of the rank directly below your next one to get it
2) You have to obtain a certain rank to record a time for the nest stage. For instance, that if you were not Ra ZAN but Bu GOU, then your time for C5 would not be recorded.
The two above statements are not true, and here is the proof:
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All this is positive since it means that you can accompany friends who are close to obtain a S-rank time (at most 420 minutes) and still get your share.