Secret
A grain is certain to keep a secret.
ひ
ひ
None
If someone finds out your secret (not from the grain though, it will certainly keep it) then your entire face will fill with heat (ひ).
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.