During their rest period, Shinji spent most of his time near camp, finding relatively secluded places to train alone.
First, he worked on thoroughly familiarizing himself with and mastering the Two-Tomoe Sharingan itself.
He repeatedly practiced activating, maintaining, and deactivating it, carefully experiencing the new sensory world opened up by the comprehensive improvements to his dynamic vision, perception, and ability to catch fine details.
He discovered that with two tomoe active, he could not only see an enemy's muscle twitches, shifts in balance, and chakra gathering more clearly and as though in slow motion.
To a certain extent, he could even predict which ninjutsu an opponent was most likely to use next by observing changes in the direction and intensity of their chakra flow at specific points along their chakra pathways.
This was especially true of B-Rank and even A-Rank ninjutsu with complex hand seals and obvious chakra mobilization patterns.
This almost precognitive ability was undoubtedly revolutionary for making decisions on an ever-changing battlefield and timing evasions and counterattacks.
Next, he began making deliberate, systematic attempts to simplify the hand seal process.
In fast-paced, high-intensity fights to the death, saving even a fraction of a second on hand seals could tip the balance between life and death.
For his first practice subject, he chose a Fire Release ninjutsu he had mastered most thoroughly and whose structure was relatively simple-the Great Fireball Technique.
At first, he tried eliminating unnecessary finger movements from the hand seal process, stripping away decorative or habitual redundancies and retaining only the few seals most essential to circulating, transforming, and releasing chakra.
Then, once he grew familiar with the streamlined seals, he began tackling something more difficult, with even stricter demands on chakra control-one-handed seals.
It was extraordinarily difficult.
Completing the cycle of circulation, compression, nature transformation,