Uchiha Shisui graduated from Konoha's ninja academy during the third great ninja war. Uchiha Shisui saw the cruelty of the war, many of the people who attended the academy with me died in the war or retired from their shinobi career but, he loathed the war and tried to protect his village Konohagakure.
Uchiha Shisui didn't voice this opinion of his as his clan had some differences with the village and it further added fuel to the flame. Luckily for Shunshin no Shisui, his team made it out of the war intact which he is extremely grateful for, but alas his happiness was short-lived as his teammate died right in front of him a year later which made him awaken his Mangekyō Sharingan.
Shisui kept this matter very close to his heart and he didn't let any other soul know this as he knew the storm this issue will lead to. Uchiha Shisui saw how his father succumbed to the injury he got in the war, slowly Shisui had to accept that his father will die but he was surprised by how quickly he came to terms with that issue.
Shisui attributed it to his participation in the war even when he made no significant contributions, he can only sigh thinking about what changes war brings to a person.
Shisui went on with his life and got proficient in using body flicker jutsu. He added his touch to the jutsu owning that jutsu that like no other shinobi, earned him the name 'Shunshin no Shisui' but still isn't widely known yet.
After Shisui has become Chunin he joined Anbu which is directly under Hokage-sama. His days went by normally, and one day he observed two kids who should be attending ninja academy training at an abandoned training field that he regularly uses.
Shisui observed the kids from a distance, he noticed a boy with Uchiha features with an Uchiha crest on his back along with a red-haired boy with blue eyes the same age as the former with a crest all Konoha shinobi on their vests and another clan symbol on his left arm which he couldn't identify.
{Sorry I've realized I didn't describe Hiroto clothes so here it is a black t-shirt with an Uzumaki crest on his back and a Namikaze clan crest on his arm along with black trousers with a red outline on the corners, I couldn't find an image anywhere close to this so that I could post}
Shisui was amazed by both the kids he could identify the Uchiha kid as Uchiha Itachi because of his fame in the Uchiha clan as a genius soon he could also place the name of the red-haired kid as Uzumaki Hiroto. He observed some days both the kids are present but on other days only one of them is present or sometimes both of them are absent.
Today just like the other days he saw both the kids taking positions he want to observe them so he moved closer to their positions and hid. Shisui suddenly saw the red-haired kid throw a kunai at him he noticed something odd about it but couldn't identify what it is. Shisui suddenly deflected it but the next moment he was bombarded by a great fireball jutsu from Itachi and a wind jutsu boosting the former Jutsu's attack power.
Shisui quickly used his signature body flicker jutsu and created after images that can be easily misinterpreted as clones. "Hey, guys.." Shisui wanted to explain to them but felt a presence from his backside so he swiftly moved away and saw Hiroto coming at him doing hand signs, he was awed by the speed of hand signs.
Shisui was now met with attacks from both front and back, so he quickly used body flicker to not have a bad impression from the kids on their first meeting.
Shisui landed on a tree a good distance from them. "Hey STOP! I am not an enemy" Shisui said to make the kids stop the barrage of attacks.
Itachi noticed the intruder's features now and placed his identity as someone belonging to the Uchiha clan. "So if not an enemy who are you then ?" Itachi interrogated his fellow clansmen. "Are you a pervert like that old man who watches spies on kids instead ?" Hiroto asked playfully after sensing Shisui's chakra.
"I'm not a pervert especially not one to spy on little kids" Shisui voiced out his innocence. "I just want to see your skills, anyway what are you kids doing here when you should be in the academy ?" Shisui gave his reply.
"How do you know that we should be in the academy ?" Itachi asked in return. "Of course, I heard about the two prodigies of the ninja academy Uchiha Itachi and Uzumaki Hiroto" Shisui stated. "And he says he isn't a pervert." Hiroto took a jab at the older kid.
"The academy is boring they don't teach us anything new, so we are sending a shadow clone" Hiroto answered. Itachi asked, "So who are you ?". "My name is Uchiha Shisui, I am a chunin," answered Shisui.
"So you are the famous Shunshin no Shisui the clan is clamoring about" Itachi said. "Yeah body flicker jutsu is my signature but even with it I don't think I can move as fast as Hiroto here," said Shisui sheepishly rubbing his head.
"You already know about us but let's get formally introduce ourselves. I'm Uzumaki Hiroto" Hiroto said. Itachi also introduced himself as "Uchiha Itachi".
Like that the three of them chatted together and Shisui also offered to help them train when he is free. "Hiroto what did you use to move behind me? Can I know how you did your hand signs at such a fast pace ?" Shisui asked.
"Shisui-san sorry I can't tell you but I will share it with you later," Hiroto said to which Shisui nodded in understanding as a ninja won't share his secrets.
Kakashi who completed a mission felt someone stealing something precious from him, he ignored it and is currently on his way to Konoha to check on Hiroto and Naruto as it had been a few months since he had last seen them.