The Third Hokage had already stated that to pass the graduation exam, one must first pass the written test. The content of this test is based entirely on the textbook.
As a ninja village, Konoha does not place too much importance on written knowledge; it values a ninja's practical combat ability far more. Therefore, even any Tom, Dick, or Harry can easily pass the written exam. If that weren't the case, wouldn't Naruto have been unable to graduate for his entire life?
Every year, the content of the graduation exam is selected from six categories: basic taijutsu, basic shurikenjutsu, genjutsu dispelling, Substitution Technique, Transformation Technique, and Clone Technique. If a class is lucky, they might be tested on Transformation, Clone, and Substitution Techniques. If they are unlucky, they might face things like genjutsu dispelling or shurikenjutsu.
Yashui had long known that this year's exam content was the Clone Technique, a skill he could already use with ease.
However, the Third Hokage is not so easily fooled. To graduate early, one must be tested on more than the other students. That is why he had Asuma come to test Yashui.
If nothing goes wrong, Asuma will likely put Yashui through all six of the aforementioned tests.
Basic taijutsu, basic shurikenjutsu, and the Clone Technique are not difficult for Yashui. In fact, these three are his specialties.
As for genjutsu dispelling, as long as Yashui quietly activates his Sharingan, he can pass the test even without doing anything, relying solely on the natural genjutsu resistance provided by the eyes.
The problem lies with the Transformation Technique and the Substitution Technique. The hand seals for these two are not difficult, and they are easy to pick up. However, applying them to actual combat requires a great deal of practice. For an average ninja, it takes at least a week of training to master them.
The difficulty of the Transformation Technique lies in perception. For a child, the sense of height and width differs from that of an adult. When using the Transformation Technique to become an adult, subjective perceptions of adult proportions can cause the transformation to look inaccurate, requiring much practice to correct.
The Substitution Technique is a low-level space-time ninjutsu with extremely low chakra consumption that allows the user to swap places with a target. Although it is touted as being able to "dodge all attacks," it is actually quite difficult to use and has many limitations.
First is the visual disorientation after using the technique. Some ninjas, due to the speed of the swap or poor selection of a target, become disoriented and lose track of their location. This is similar to motion sickness and can only be overcome through practice.
Second, and this is the greatest difficulty and flaw of the Substitution Technique, is that the target must share similar characteristics with the user. For example, the log that appears most frequently in the original series became a target precisely because its volume was similar to the user's.
However, it is not always possible to find something with similar traits to the user everywhere. Sometimes, it takes quite a bit of effort to find a suitable object. Speed in finding these targets can only be improved through practice.
Often on the battlefield, it is difficult to find something to substitute with. Some ninjas raise animals or use clones to serve as substitutes, but most ninjas are simply left helpless.
Therefore, it is not that the Substitution Technique fell out of use in the later stages of the series; it is that the nature of the battlefield changed, making it unusable. (Trying to justify Kishimoto's inconsistent world-building...)
In short, it is unrealistic to master these two techniques to the point of practical combat use in a single day.
At this moment, Yashui recalled that when using the Sharingan, he would subconsciously gain knowledge he didn't previously possess or wasn't proficient in. It was as if he were gaining someone else's memories and proficiency...
There was no other choice. Even though he didn't know the principle behind it, it was worth a try if it meant graduating a year early.
After dinner, Yashui locked himself in his room and drew the curtains, leaving the house in darkness. After being abducted by the Konoha Anbu yesterday, Yashui was extremely cautious, keeping the lights off whenever possible.
Yashui extracted some chakra and activated his Sharingan. The pitch-black room suddenly became clear in his eyes. The boost the Sharingan provides to vision is no joke.
"Substitution Technique, Transformation Technique... Substitution Technique, Transformation Technique..." Yashui repeated these in his mind. Three minutes later, the relevant knowledge for both techniques flowed into his consciousness.
Seeing that he had obtained what he wanted, Yashui deactivated his Sharingan. As a kekkei genkai of the Uchiha clan, the Sharingan consumes a significant amount of chakra.
"Transformation Technique!" Yashui turned on the room light and performed the technique in front of the mirror.
"Poof!" After a puff of smoke, a person identical to the Third Hokage appeared in the mirror.
"The Transformation Technique was a success." Yashui felt more relaxed about tomorrow's test. "Next is the Substitution Technique."
Yashui looked around, but there was nothing suitable to use as a substitute.
"Should I try a toy?" Yashui looked at a life-sized Enma doll in the room.
"Substitution Technique!" After performing a few hand seals, Yashui immediately activated the technique.
Another puff of smoke. Yashui's body and the Enma doll swapped positions.
Both techniques were solved easily. He should be able to pass Asuma's test.
Seeing that these ninjutsu were "learned" so easily, Yashui lay on his bed, feeling satisfied.
"No, everything has been too smooth since I entered this world. If I keep using these shortcuts to gain power, I will eventually get used to getting things without effort... I'm already becoming lazy..." Yashui felt a sense of crisis. "From now on, I should try not to rely on the Sharingan."
On the path outside the Third Hokage's house, Asuma and the Third Hokage were taking a leisurely stroll.
"Old man, stop seeing me off. You should go back. You still have to look after Konohamaru and Yashui." Asuma lit a cigarette and took a deep drag.
"It's fine, they are both independent children. In seven or eight years, we will be relying on them to hold up Konoha." The Third Hokage also pulled out his pipe. "Asuma, when will you start smoking this kind of tobacco like an adult?"
"These rolled cigarettes are the progress of the times."
"Speaking of which, what do you think of Yashui?" The Third Hokage changed the subject. "That child suddenly requested to graduate early."
"Don't worry, I'll try to make the test as difficult as possible tomorrow," Asuma said, appearing indifferent. "Uchiha Yashui has been getting very close to Uchiha Sasuke lately. The power of the Uchiha clan once nearly brought disaster to Konoha. Now that the two of them are so close, I wonder..."