Genma held up a small palm-sized piece of paper. "Do you know what this is?"
"It's how you determine what element you have affinity for. I have to activate my chakra and what the paper does in response indicates what element; wind, fire, earth, water or lightning."
Satisfied, Genma handed her the paper. Taking it she felt simultaneously nervous and excited. With all five fingers touching the paper, she closed her eyes and activated her chakra. After a moment she opened her eyes and saw that the paper was wet.
"Water," noted Genma pensively. "Interesting. Now, show me what you've done to improve your chakra shield."
Obligingly Atsuko immediately created a neat oval shield that matched her height and width. It was a transparent blue that shimmered with the chakra energy of which it was composed.
"I've learned to shape the edges more precisely and I've figured out how to change its size." To demonstrate, she increased the shield to twice its size and then shrank it down to the size of a plate.
"Good," said Genma, nodding in approval. "That can come in useful. Can you create one in each hand?"
She shook her head.
"Hmm," he muttered. Then suddenly he spat his senbon at her, the metal needle flying towards her face in an instantaneous blur.
Had she not been practicing her shield, she probably wouldn't have thought to use it. But she did; her reflexes allowed her to throw up a shield large enough to cover her face just in time for the senbon to bounce off the glowing chakra field.
Her heart pounded and her lungs were suddenly empty of air as she thought of how close that had been.
Genma, however, looked pleased. "Good. You have the makings of an excellent defense."
"Did you have to aim at my face?" she asked, irritated.
With an unapologetic shrug, Genma replied, "Best way to test your reflexes. As you no doubt have noticed, I've been conducting a comprehensive test to see where you stand in terms of physical and chakra-based abilities. You certainly have the potential to progress further.
"Because of the shortage of jonin, Shirakumo will rarely be able to participate in many missions with your genin team. He will not be able to help with your individual training. Since I'm familiar with your skills, I'll be able to fulfill that role. However, I will also be absent often, so the burden is on you to complete what tasks I assign you. The path towards becoming a shinobi only gets harder. Each step requires greater strength, both physically and mentally. You will be pushed to your breaking point and then beyond. I will give you tasks that you can work on during and between your missions. This is how you will learn and create new jutsus. Your missions will teach you tactics, situational awareness, and teamwork where you will eventually be able to apply your new abilities."
Atsuko nodded slowly. "What jutsus will I be learning?"
"To start with, your chakra shield is decidedly useful, as I have said. If you can infuse it with your element, water, you will have an even stronger and malleable defense. After that, there are any number of water-based jutsus you can learn or develop on your own," he explained. "Eventually you can learn to use a second element, but that is advanced jonin-level. It's not worth thinking about now."
"So," Atsuko said, "you're going to be like my personal tutor." She grinned. "I can call you Genma-sensei!"
Genma winced. "Jeez." But she saw the corner of his mouth twist into a hint of a smile.
=/=
Early the next morning Atsuko waited by the village gate. Shirakumo-sensei had left a message for her to join his team there: they'd already been assigned to a mission for that day and jumping right in would be the best way for her to become acquainted with the team and they her.
The sky was clear, the weather warm and Atsuko had Genma's pouch attached to her waist and her new set of senbon tied around her right thigh. Physically she was ready but mentally…
Finally from the village she saw three figures approaching. The tallest wore a short-sleeved version of the jonin uniform with his protector wrapped around his forehead. His steel grey hair was pulled into a high pony tail and his eyes were a weary but narrowed black.
"You must be Atsuko," said Shirakumo. "Good. I appreciate punctuality."
One of his companions, a young man with spiky black hair snorted and pushed his glasses up higher on his nose.
The second, a girl Atsuko's age with unruly red-brown hair, narrowed her eyes in response and slammed her elbow into the boy's side. He grunted then threw her a glare as he adjusted his glasses again.
Shirakumo sighed. "I'll introduce your team. This is Toshikazu Gisuke, our medical ninja." The young man nodded politely but with an aloof aire about him. "This troublemaker is Zensaku Yukina. She's loud, obnoxious, and perpetually late." Yukina grinned and waved. "These two constantly provoke each other. I expect you to help me maintain the peace."
His tone was so serious and weary that Atsuko struggled not to smile. "You can count on me, sensei."
Yukina groaned dramatically but Shirakumo ignored her. "Good. Let's go, we have a substantial journey ahead of us."
=/=
Along the way Shirakumo explained their mission. It was a C-ranked escort for a merchant from Fire Country to the Land of Wind. The main threat was from thieves; there wasn't any expectation of enemy ninja being involved. There was a second part to the mission, too, as they were to deliver a letter from the Hokage to the new Kazekage, Gaara of the Sand. The letter was to further cement relations between the two shinobi villages.
The merchant lived on the edge of Fire Country which meant they had a full day's walk ahead of them. So Atsuko had plenty of time to get to know her teammates.
Yukina was the most outgoing of all of them. Loud and talkative, Atsuko could tell Gisuke and Shirakumo had given up on getting her to be quiet. But Yukina was no stranger to combat and carried a tanto attached to her lower back that she was well versed in using lethally. There was also a raw ferocity behind her green eyes that told Atsuko she was a force to be reckoned with. She was a fire user and was learning from Shirakumo how to use it in conjunction with her tanto.
Gisuke was the complete opposite of Yukina. Quiet and reserved, he was one of the first medical ninja trainees to be assigned to a genin team. His training was still incomplete, though, and he was still learning from a medical ninja instructor like Atsuko was learning from Genma. In addition to his healing skills, Gisuke was also a sensor type that could detect and distinguish chakra. He also apparently had some talent with genjutsu. All this made him extremely confident, however, and he was constantly pushing his glasses further up his nose in a decidedly snobbish manner. It seemed mostly directed at Yukin, however, with whom he constantly bantered and argued with. He seemed to have reserved judgment for Atsuko.
While Yukina and Gisuke were having one of their arguments, Atsuko took the opportunity to walk next to Shirakumo.
"Have they always been like that?" she asked.
"Since their Academy days," he affirmed. "They constantly go at it, but they've learned to stop when necessary. They make a good team when they're serious."
"I hope I can learn to fit in," she said.
"You will, after you've had time and experience. You will learn how to complement each other's strengths and account for each other's faults." A strange look of pain crossed his face.
"What is it?"
Shirakumo glanced behind them at Yukina and Gisuke, who had stopped speaking to each other in a silent stalemate.
"It is nothing," he replied tersely. And the conversation was over.
Shirakumo was in one of the fillers later in the anime, if you want to see what he looks like. It was the one with the old genin man.