On a separate post, just in case some people are picky about that kind of thing. As a warning, this contains spoilers up until chapter ten of Kanata's story!
Out in the far reaches of space is a most peculiar world. Where magic and science mix, where humans, demons, and aliens all live. It's a mysterious place too--you never know what may float your way! Anything and everything from elsewhere can drift towards this world. Food? Yup. Toys? Yep. Furniture? Yes. Junk? You betcha. Whole buildings? Schools? Libraries? Dungeons? Of course! There's just simply an infinite amount of fun and possibilities to be had in this strange world.
It is known as the "Netheruniverse"--
"No... no, I don't want to!"
"Suzaku! What is the meaning of this!? It's far too early to put Lord Kanata through this!"
"There is no other choice. Lord Shuten's power is weakening day by day. At this rate, he'll eventually..."
"... I... I still won't be able to do anything..."
"This is the duty that's been imposed on you, Lord Kanata. You may think it harsh, but... please accept it."
"... ah! Wa-wait! Gah-!"
"Lord Kanata!"
"Aaaaaaaaagh-!"
--it is where our story begins.
Fortunately and unfortunately, the ceremony above fails. Kanata is not forced into his duty to become High Demon Emperor, but he's thrown in the castle's gaol for another go later on, loses his awesome demonic horns, and gets a pair of adorable puppy ears instead. But luck stays with Kanata--while one servant may have betrayed him, one is still on his side. Tsubaki frees him from the gaol, and they both escape from the castle into the castle town.
It is here that they discuss things, try to obtain information, and try to stay undercover so that Suzaku doesn't locate them again. ... well, more like Tsubaki tries to. Kanata mostly ends up trying the food at different food stands, ignoring whatever Tsubaki says, all the while moping and being a little bratty about recent events. When Tsubaki finally gets fed up and pulls on Kanata's ear to get his attention, he spills everything.
No matter what Tsubaki says, he's not going back to the castle. He's not going to become High Demon Emperor. Ever since he was a kid he's been holed up inside the castle, training for when he became Overlord and forbidden from going outside. He doesn't know what it's like to live freely! This is his chance!
Much to Kanata's surprise, Tsubaki puts his worries to rest. She doesn't mind if he doesn't become High Demon Emperor. Would she have helped him escape, if that was her intent?
"... oh. I guess that's right."
With that sorted out, they continue walking about the castle town--until something worrying catches their eye.
One of the flotsam hovering over the Netherworld threatens to crash into the town and destroy some of the shops. Kanata shows some concern, but the Netherworld has plenty of shops, Tsubaki reminds him. No one's gonna miss one or two. But! But! An idea rings about in Kanata's flower-filled head. The entire purpose behind becoming High Demon Emperor is to prevent this very thing--to keep the all the objects/flotsam from crashing into and destroying the Netherworld--right? What if he travels to all the places that get dangerously close and sets them adrift back into space? This way, he can do what he's always wanted to do--go on adventures, of course--protect the Netherworld, AND he doesn't have to become High Demon Emperor anymore! It's like getting two birds with one stone! It's okay if he does that instead, right?
... and Tsubaki hesitantly agrees, she supposes that would be fine.
So Kanata's adventures begin! And, oh, how thrilling they are! Traveling from flotsam to flotsam, exploring new places, finding treasures, fighting monsters... and what would an adventure be without more friends? On his quest to have awesome fun times Kanata meets a space pirate who has a taste for sweets (as well as a huge squad of prinnies) and a carefree ghost who runs an inn (and sometimes seems to not be self-conscious at all about how she's, uh, dead).
Of course, Kanata's plan isn't as simple as he thinks--or, well, maybe it is--there's still people who want to force him to become High Demon Emperor, whether he likes it or not. Suzaku is the obvious antagonist here, turning his weapon towards the group repeatedly and trying to get Kanata back to the castle. And he's not even willing to explain his reasons when he loses! I mean, when you say that you're not doing it to protect the Netherworld, but for your own reasons, that's kind of a big deal! ... but even when they beat and have Suzaku unable to run away from them, Kanata still lets him go.
Oh, but he's not the only opposing force that Kanata and company have to deal with. They meet and often clash with a goddess (with very funny-looking pigtails, Kanata notes) and some lame dark hero. They, too, want to protect the Netherworld--well, the goddess, Rizelia, does. (Lukius is just tagging along because Rizelia's threatening him with violence, what he REALLY wants is to take over the Netheruniverse.) But unfortunately for Kanata, Rizelia is less about destroying the gravitational field of flotsam that hover too close, and more about arresting Kanata so he can be put through the proper ceremony.
This sounds annoying, but there's a glimmer of hope for change! Shortly after the two groups are forced to team up together to face a laser-shooting-dragon, they encounter one another again as enemies once more. But something is a little different this time.
"You want me to become High Demon Emperor that badly?" Kanata asks sadly.
Rizelia snaps at him in return. "That's right! It's your duty, isn't it? So why do you keep running!?"
"... if I become High Demon Emperor, I'll lose my freedom."
"... what do you mean?"
Kanata quietly explains that the process is similar to a sacrifice--he'll have to give up his powers and his life. If he does go through with it, he'll be able to protect and watch over the Netheruniverse, yeah, but he won't be able to even walk around anymore. Seeing the castle town, seeing so many places... he's started to think that he wants to take care of and protect this world. But there's still so many places and things he wants to see too.
Rizelia hesitates. She wants to protect this world, but is it fair to take away someone else's life in order to do so? She's not sure if she could go through with it now.
Having realized that, Rizelia admits defeat and runs off.
Now it's Kanata who is having doubts about what he's been doing. "... Tsubaki, I... would it be better if I became High Demon Emperor?"
Tsubaki assures him that it'd be just fine if he didn't, but Kanata's reply is still quiet and sad.
It isn't until a little later on, while he reflects on all the objects floating around in the sky, that Kanata comes to his resolution.
He'll protect the Netherworld in his own way.
Oh, but there must have been an an accident on the way to the next area. A glitch in the system, a wormhole, maybe the alignment of all the flotsam was just right!
Because Kanata ends up in Paixao instead.