This fight showed Ousen's weakness.
Ousen's basic strategy is based on terrain, bait, lure the enemy, and finally ambush. It helps Ousen defeat Kyou En and Ordo.
During the Zhao invasion arc, Ousen relies on intelligence and information warfare to stay one step ahead of Riboku, then relied on the trio's awakening to defeat Riboku
This time, Riboku decoded Ousen. That's why Riboku chose the battlefield in the plain area, assigned the central role to Seika, then baited Akou to trap Shin and pulled Ouhon away from the central battlefield, giving Enkan 70k soldiers with the task of holding Hishin units and reinforcements, buying time for SeiKa, eliminating Ousen's contingency plans.
Many people found the arc disappointing because of Ousen's passivity. Unfortunately, there wasn't much Ousen could do when he found himself in this situation. It also confirmed that Renpa's point of comparing Ousen to Hakuki was incorrect. Ousen has not yet reached Hakuki's level