The Rules Universe consists of a series of yaoi stories created by Kano Miyamoto, which mainly revolves around Hikaru, his love interests, and friends. Hikaru's high school friend and love rival Ryuu debuts in Please, while Hikaru himself debuts in Kiss. Hydra and its doujinshi revolves around Ryuu, Hikaru, and Hitomi and their high school years. Lovers and Souls covers the story of Hikaru's prostitute friend Tooru and Tooru's sempai, Matsuoko. Rules and its doujinshi focus on Hikaru, Yuki, Tooru, and Atori.
As of 2011, the Rules series Timeline is as follow:
- Please (chapter 5)
- Kiss After
- Hydra 1+2+3+4
- Hydra 5+6
- Hydra 7+8
- Blue Film
- Hydra 9+10+11
- The Days Before
- Real Thing
- Hello Again
- Lovers and Souls
- Dreamer's high
- Rules volumes 1 & 2
- If Winter Comes, Can Spring Be Far Behind?
- Rules volume 3
- Song Birds
- Another Day on The Planet
- Another Rules Story
- Double Trouble
Hydra: When Ryuu transfers to Hitomi's school, he leaves an immediate impression on him. Curious about rumours of a full-scale tattoo on Ryuu's back, Hitomi starts getting closer to him. Before long, the friendship and fascination Hitomi feels for Ryuu start developing into more, but before he has a chance to come to terms with his feelings, Hikaru appears on the scene.... and he has his eyes set on Hitomi.
Lovers and Souls: Tooru is a young model who becomes a gay prostitute because he doesn't care enough about himself. However, he's starting to fall for his sempai. Can Matsouko save him?
Rules: Yuki, a high school student, is confused about his sexuality. He meets Hikaru in the sleazy gay district, and sleeps with him. They begin to play at being lovers, but Konoe's heart belongs to Atori, his friend and classmate. Can Yuki come to terms with his sexuality and reveal his feelings to Atori, and where do Hikaru's true feelings lie?
- Accidental Murder: Part of Ryuu's past, and responsible for his Angst
- Age-Gap Romance: There's a 10 year difference between Hikaru and Yuki.
- Anchored Ship:
- Hitomi and Ryuu. They probably got together. Probably.
- Reunion Hug
- The Atoner: Zigzagged with Itou.
- Bi the Way: Everyone except Yuki it seems, something which is lampshaded by him.
- Boys' Love
- Chekhov's Gunman: Hikaru in the beginning of Hydra. He starts as a Generic Guy in the Gang of Bullies and is not until a few chapters later that we learn his name.
- Class Reunion: Lampshaded by Satou when Hikaru, Ryuu, Hitomi, and her reunite six year after high school. Hikaru invited Itou, but he declined.
- Dropped a Bridge on Him: Matsouko.
- Fetish: Ryuu's tattoo, especially for Hitomi.
- Friends with Benefits: The relationship between various of the characters with varying degrees of success.
- Gang of Bullies: Unique in that Hikaru was part of it. The leader, Itou bullies the main characters because he is a Stalker with a Crush of Satou. He pulls a If I Can't Have You... on her, which is used as an excuse for her Put On A Plane status.
- Gender-Blender Name: Hitomi is a guy.
- Good Scars, Evil Scars: Hitomi by his eye due to a motorcycle accident that happened before the start of the story.
- Hairstyle Inertia: Averted. Everyone changes hairstyle and sometimes hair color as time passes on.
- Hooker with a Heart of Gold: Male example with Tooru.
- I Want My Beloved to Be Happy: Hikaru for Hitomi
- Looking for Love in All the Wrong Places: Hikaru to a certain extent.
- Love Triangle: Apart from the love triangle in Hydra, there is a nice romantic square in Rules.
- Second Love: Yuki for Hikaru and vice versa; Atori for Tooru.
- Seme/Uke: Averted, in that you can't tell who is which and that once in awhile they switch roles.
- The Smurfette Principle: Satou is the only female with some importance in the Hydra manga. That is until she was Put on a Plane. The Plane Came Back: for a reunion with Hitomi, Ryuu, and Hikaru at the end of Hydra.
- ¡Three Amigos!: Hitomi, Ryuu, and Satou somewhat have this dynamic for part of Hydra until Hikaru was introduced and Satou was Put on a Plane.
- Yakuza: None of the characters are Yakuzas but Ryuu's father, who is a tattoo artist for the yakuza, gives Ryuu a tattoo which leads other students to believe that he belongs to the yakuza.