I am so sorry for the wait. Work and school got in the way and I had thoughts of writing other adventures in later chapters. It's just that it had been 3 chapters already and I felt that this fic needed a lair-chapter sooner or later, otherwise it wouldn't be the same. I had a really hard time trying to figure out how to write this, which is another part of why I got really slow on updating. Hopefully, this won't be the case later, but fingers crossed.

Heads up on this chapter: Introducing a new character, and other additional facts about my fic-verse at the end at the chapter.

Tokyo: Shibuya's Sewer Life

Down in the tunneled depths of Shibuya, among the dark and dimly lit subway lines that interconnected like layers upon layers of spider webs, a spacious niche of concrete chambers sat nestled within the shadows. It was designed to be rather simple, being composed of square or rectangular rooms that stood about seven feet in height. They appeared to be arranged in almost a ring-like fashion, only that it wasn't so much circular as it involved rooms connected to the outside of a hallway, which itself encircled a much wider room in the center. At every side in the room-laden bordered hallway, there was at least one room that was wider than others, though nowhere near as wide as the main room in the center within the square hall. That main room sat at least a yard lower than the rooms surrounding it. It only remained connected via the four modestly sized sets of stairs that extended downwardly from each narrow path making up the outer square. As if the layout was not complicated enough, that same atrium was surrounded by its own dividers. They weren't walls as they didn't reach all the way up to the ceiling, but only were about a yard tall, only high enough that one had to grab at the edge and launch themselves up with both a pull and a little leap in order to take a peak over to the other side.

"Hah! I win again!" cried out a youthful boyish voice. The source of the cry came from a boyish orange-masked turtle, one who sat down cross-legged while raising his arms up in the air, his hands balled up in pumped fists of victory. A disgruntled growl came from the other red-masked turtle facing him. He was lying down on his belly, his arms clenched in fists that shook with irritation. His green eyes were furrowed and held a piercing glare at the pile of cards that lied on the cold concrete he and his little brother were on. The orange-masked turtle reveled in his energy rush, "Looks like I'm still the King of the Cards, Hiro!"

Hiro, the red-masked turtle, could only slap the cards he held in his hand down hard on the hard floor. "Well, I still think you're the dirtiest 'King of the Cards' to date!" he exclaimed. He pointed a finger at his little brother's face right between the eyes. "One day, I'll expose you for your treacherous tricks, Mon!"

Mon only drooped his eyelids smugly while inching himself closer to Hiro's face. "Oh, I'd never betray the art of card-bushido. I'm just naturally that way." Mon went further to push a fingertip on Hiro's forehead, prompting the hot-blooded turtle to tremble as he built up steam as Mon continued his spiel, "Face it, Hiro – in the Card Province, I'm Yoshitsune and you're Yoritomo."

"That's it!" Hiro growled in his mind. But before he could go further with his thought, he detected Mon's eyes suddenly widening while looking back down at the card pile.

"Hey! That's my lucky draw! Give those back!" Mon exclaimed diving for the bunch of cards that he put down which were currently being nibbled on by a smaller brown-shelled box turtle. Mon only managed to snatch back two of the cards before the tiny turtle began crawling off with the other three still in its mouth. The sight of that made Hiro change from growling to chuckling, taking entertainment in his little pet turtle giving his little brother difficulty. Mon scrambled after the turtle and managed to grab at one card still in the little turtle's mouth, but ended up wrestling with said turtle for the card. The little turtle slipped away and out of Mon's grasp and kept crawling.

"Great job, Spike," Hiro silently congratulated his little pet.

Meanwhile in a bricked garage, a purple-masked turtle was wearing goggles and holding a welder while working on a machine. It had been a while since he began placing, drilling, and now welding several parts together in his quest to build a new invention. Once he had finished, he lifted his goggles off his eyes and let out a sigh of relief at what he had built.

"Phew! Okay then, all joints are together, motherboard's secured, energy routers and re-routers are connected, and outer plating melted in place." He followed the set of cables attached to the device all the way to a generator with a big switch on it. "Time for a test run."

"Uh, Basho?" a hesitant female voice cut the air, "I'm all for seeing your latest invention, but I don't really get why I'm being involved in this test right now." The girl with her yellow and black shirt, light grey hoodie, blue denim jeans, and black sneakers, sat on a swivel chair with another piece of the mysterious device on her head. The bottom tips of her light-tinted and pigtailed hair were tucked away under the collar area of her hoodie.

"No worries, Uzuki," said Basho, the purple-masked turtle. "I'm just testing out my custom-made infiltration console." He typed away at a nearby laptop. "If my calculations are correct, it should be able to function effectively as a remote control for drones and probes we can use to spy on the Kraang and other criminal operations."

"So, you're building this because you want to sneak into TCRI, right?" was Uzuki's suspicious questioning.

"Well," Basho answered hesitantly, "that, and I'm looking for other ways to improvise on our ninja approaches." He then moved to the switch on the main console of his device. "Okay, turning on the central unit in three, two, one…" He pulled the switch. The machine hummed as a pink light began brightening on some of its glassy parts. Seeing the piece held up by Uzuki's head light up too, he then spoke to her, "Hey Uzuki, can you try thinking of a command?"

Uzuki sat, ruminating on what kind of command Basho wanted her to think of. Looking at the bipedal turtle-like robot before her, she closed her eyes and then tried to formulate a message to send through the remote-controlling headgear. "Go." The robot took a left step forward, then a right step, alternating continuously so that it now began walking towards Uzuki herself. Seeing the robot beginning to get close to her, she let out another command. "Stop." The robot, instead of obeying her, kept walking in her direction. "Stop," Uzuki repeated herself, but the robot stayed in motion. "Stop!" Uzuki exclaimed frantically, shuffling backwards off the chair she was sitting on to put further distance between herself and the machine. The abruptness of having to back away caused her to fall to the concrete floor on her backside, and Basho scrambled to try and stop the robot from walking over his human friend, the noisy clattering of equipment drowning the atmosphere of the garage.

Meanwhile, in a room that appeared bigger and taller than the others and decorated with vibrant-colored carpets and mats with traditional Japanese wall decorations, Hoku the blue-masked turtle was quickly moving between stances of various forms and postures, maintaining his current position below the canopy of the tree that stood behind him under the light of a sewer grate up above. One leg up, then down with another leg up, arms bent up one way, an arm bent down another way, and so on. He was only practicing his katas, having nothing better to do. Of course, he could join his brothers with whatever fun things they were doing, but he just wanted to get his practice done first. He was going through a few more sequential forms when he heard a deep older voice jolt him out of his concentration.

"Hokusai"

He turned around to find himself facing the tall and authoritative figure of his father walking towards him, a bipedal brown rat mutant wearing a dark red floral pattered kimono with a green jade cane in his right hand. Hoku immediately stood up straight and bowed in respect. "Sensei," was his quick and curt response, being as polite to his father as ever. He maintained that pose even when his rat father had stood right in front of him and placed a hand on his shoulder. The rat man, who stood tall and imposing with one arm firmly holding his staff and the other held towards his turtle son, gave a gentle smile that was both out of pride and exhaustion.

"My son, you have been training for some time now," he spoke to Hoku, his tone of voice deep and reverberating yet calming and without aggression, "You have already practiced the forms enough times. It is about time you take a rest."

"I understand, Sensei," Hoku said, "I just feel like there's something missing every time I demonstrate it to myself. I'm only repeating it to make sure it's exactly the way you taught it to me." He looked up slightly to look Sensei in the eye.

"Hokusai," Sensei spoke further, "You spend so much time trying to do something perfectly when there are other aspects you could give attention to as well." He turned and walked to the side to look at a painting that seemed part Ukiyo-e and part European-styled Art Deco, a name scribbled 'Michiru Hiruta' (昼田 満ちる) at the bottom corner. "Be careful not to put too much energy and strength into your fights. Otherwise, you will have none left when it is time to recover."

Hoku did not seem to understand why his master and father was saying this. "Sensei?"

Sensei turned back to look at his eldest son. "Your brothers are out there enjoying life and making memories, but they are missing you from the experience. Why don't you rest and have fun with them for a while?" He gestured to the outside of the training dojo with a motion of his head.

Hoku looked out in the same direction Sensei had motioned towards. In the main atrium of the lair, he saw Mon and Hiro fooling around with playing cards. He saw Uzuki peering over Basho's shoulder as he fiddled away at a robot part. He looked back to the dojo; apart from Sensei, he was training by himself, and he remembered that he seemed to do that almost every time they finished a patrol or a mission recently. He justified it to himself as being prepared in case threats come back stronger and smarter, given him and his brothers' tendencies to pull tricks on their enemies. On the other hand, maybe it was just a side effect of exposure to Tokyo surface culture – one could never be 'good for now,' as work, progress, and improvement advanced no matter how long or still one sat. Hoku personally couldn't find a reason to take a break when he knew evil never did. In fact, part of him remembered Sensei sharing how he empathized with how most humans living in Japan took top priority with their innovations, considering they were all living on an island that often bore the brunt of the Earth's restlessness.

But as Sensei had also mentioned, there did come a time when a period of calm inevitably happened between the storms and one ought to make the most of it during that time, regathering enough strength to weather the next storm that comes their way. Knowing that he needs his brothers as much as they need him, Hoku sighed. Maybe it's time he settled down a bit. "Alright," he looked back up at his taller rat father, "I guess I should spend time with them. It'd probably be a good chance to reflect on my techniques anyways. Arigatou-gozaimasu, Sensei." He then turned to leave for the lair atrium, though not before stopping without turning around to hear Sensei tell him one last thing:

"Remember, Hokusai. Even a Kappa can get carried away by the river."

Hoku stood for a moment after hearing what his father said and then turned back to leave, calling out to Mon and Hiro in the middle of their antics while sensing Basho and Uzuki watching entertainingly from the other side.

Introducing Master Splinter, who goes by 'Sensei' here. In the 2012-cartoon's Japanese dub, he's voiced by Takayuki Sugou (菅生 隆之).

Other Fun Facts:

The Lair is located in the Shibuya ward of Tokyo. Where exactly, I'll leave that to your imagination.

The training dojo looks exactly like the one in the 2012-show, with the exception of the Ukiyo-e/European Art Deco painting hung on the wall.

TCRI is still a New York-based corporation in this fic. Its main/original HQ is in Brooklyn, but has expanded internationally. Uzuki mentions TCRI's Tokyo branch, which will still have Kraang activity. I decided to place it somewhere in Tokyo's Chiyoda ward.

Spike, Raph's (or rather Hiro's) pet turtle, is still called Spike here (スパイク). Just a nod to the prevalence of Japan's westernized influences.

Bushido (武士道) means "the way of warriors." It's a collective term for ideals and honor codes making up the samurai way. It's like Europe's concept of chivalry.

Yoshitsune (源 義経) was a military commander of the Minamoto Clan between the end of the Heian Period and into the Kamakura Period. He is considered one of the greatest and most popular warriors of his time, along with being one of the most famous samurai warriors in Japanese history ever.

Yoritomo (源 頼朝) was the founder and first leader of the Kamakura Shogunate, which was the first military government to take control of Japan in the feudal era. He is also the half-brother of Yoshitsune, being a member of the Minamoto Clan. He was assisted by Yoshitsune in taking power and establishing his rule.

The name "Michiru Hiruta" (昼田 満ちる) is one I created based off the real life painter Ichiro Tsuruta (鶴田 一郎) who's famous for his painting style which combines Japanese Ukiyo-e with European Art Deco.

"Even a Kappa can get carried away by the river" (河童も川流れ -kappa mo kawa nagare) is a Japanese proverb that effectively means "anyone can make mistakes, even experts," also as warning similar to "pride comes before a fall." It's a variation of a more well-known proverb that has the same message, "Even monkeys fall from trees". (猿も木から落ちる -saru mo ki kara ochiru)

"Arigatou-gozaimasu" = "Thank you very much" (alternative short form: "Arigatou" = "Thank you")