The Way of the Bow is Ishikawa Tale 4 of 9, the last Act 1 part of his storyline, where you defend Hiyoshi Springs from Tomoe's attack. It is worth doing early because it gives you the Flaming Arrow, plus the Charm of Immunity and the Storming Falcon vanity gear for your half bow.
Part 4 of 9 in Ishikawa's Tales
Part 17 of 66 in Tales of Tsushima
Tomoe is leading an attack on Hiyoshi Springs. Meet Ishikawa at the dojo. He is full of regret for having trained her, but Jin pushes for action rather than guilt. Follow him toward the town and talk with the peasants caught up in it. Then survey the battlefield and fight off the Mongol force before reporting back to the sensei.
Go to the dojo and talk to Ishikawa. Ride with him and talk to the peasants. Ride on with him. Scout the battlefield. Beat the Mongol force. Talk to Ishikawa.
Archers in Ishikawa's tales shoot without the usual warning and fire faster than normal, so deal with them early. Once you have the Flaming Arrow, it is yours for the rest of the game.
Image: Sucker Punch Productions / PlayStationThe Tale of Sensei Ishikawa
The Tale of Sensei Ishikawa is the Act 1 story tale where you recruit the archery master Ishikawa. It gives you your first bow, the Half Bow, and opens the Ishikawa side storyline as Ishikawa Tale 1 of 9.
The Past Never Passes
The Past Never Passes is Ishikawa Tale 3 of 9, an Act 1 side tale in Hiyoshi. Tomoe's archers have ringed Hiyoshi Springs ahead of a Mongol attack, and you scout the area with Ishikawa and clear bridges along the coast. It rewards the Charm of Precision and 2 Silk.
The Sensei and the Student
The Sensei and the Student is Ishikawa Tale 2 of 9, an Act 1 side tale in Hiyoshi. You and Sensei Ishikawa start tracking his former student Tomoe through Mongol archer positions and free some prisoners. It rewards the Charm of Efficiency and 2 Silk.
Dreams of Conquest
Dreams of Conquest is Ishikawa Tale 5 of 9 and the first of his Act 2 tales, starting at the Akashima Survivor Camp. You rescue a pinned-down Ishikawa and raid Tomoe's archer training camp for clues. It needs A New Horizon done and rewards the Charm of Precision and 2 Silk.