This dj takes place in the middle of chapter 11 as well, but focused on Taira and Hitomi instead, with a very short Ryuu x Taira fantasy for those who were wondering what would it be like.
SPOILER FOR HYDRA
Timeline-wise, this is after their breakup and before Ryuu coming back.
Now we're getting into Rules territory.
Rules stops being about Ryuu and starts being about Taira.
So if you're not interested in Taira as a character and don't what to see more of him, you can stop reading here. But if you want more of him (and plenty other new characters), definitely continue.
This dj takes place in uni, with Taira's heart still trying to heal.
We're now building up for the next "main story" - Rules.
In chapter 1, we meet Shinomiya Tooru and he is the protagonist, with a cameo from Taira Hikaru and Shige - another new character. After chapter 1, read 1.5 which is a prequel to chapter 1, but it hits harder when read after.
You can skip chapters 2 and 3, as they deal with a couple that never shows up again.
After 1.5 read 3.5 called Fragile and then move to Vanity below.
This takes place right after 3.5 and is the gateway into Rules.
It's skippable, but if you like the idea of Tooru x Hikaru, you should read it.
Here we go!
The second main story and for once you can read everything here in one go.
BEWARE that this story includes adult x minor relationships. You should stop here if that makes you feel uncomfortable (understandable, I almost had a stroke when I realized the love interests are 17. I stopped reading here because I'm not interested in this kind of relationships, but the rest of the djs are still in order, I think).
Rules Dj - Hello Again