Night mode is useless, people shouldn't be trying to sleep while you are reading or playing on the internet as that is just inconsiderate!
on here: all the way at the bottom there is a tab that says 'flat awesome' click it and choose 'flat awesome dark'
Dunno about that site... it’s all in japanese. Can’t see an obvious night mode option, though, but again, it’s entirely possible that it’s somewhere there and I just can’t read it.
Edit: Should mention that this is for syosetu. Everyone else already mentioned the NU/NUF one. Yeah, there's an menu for that. In the upper right hand corner of the site, there's a button that says "表示調整". Click it and you'll see a dropdown that says: 配色 = Color scheme 指定なし(作者設定優先) = Not specified (Up to the author) 標準設定 = Standard ブラックモード = Black Mode ブラックモード2 = Black Mode 2 通常[1] = Normal 1 通常[2] = Normal 2 シンプル = Simple おすすめ設定 = Recommended Click whichever one you want. You can see how it looks when you click on each.
If you want to change themes on NU (novel updates) and NUF (novel updates forums) Spoiler: To go dark on NU {} Spoiler: To go dark on NUF {} {} And click on the save button