Hello, I'm new here. I'm currently studying N5 and I'm having problems doing the grammar because it's full of N4 and Higher Kanji with no furigana. Are we supposed to know this? I also tried mixing N5 and N4 together and got Kanji from N3 and higher. Here's an example from an N5 sentence with N3 vocabulary (ちゅうもん) and no furigana to read it.
The site should show furigana above all Kanji's that you do not know by default (e.g. at least what the site believes you do not know). You can check which Kanji the site assumes you know by going to Study Library->Kanji Index and then click your way through the JLPT levels or whatever categorization you like to work through best. You can change the "known"/"unknown" status of each individual Kanji there as well. If you believe that there was a general error and you want to have everything reset,マイコー (creator behind this page) can hopefully help you with that.
Go to Settings > Kanji > Level before joining renshuu. Then click customize.
Currently, it is set to N3. That suggests that you've studied all the n3 terms, which I believe you are not at (based on the other post). Change that to N4, then the n3 kanji will no longer appear as black.