Isao Kachidoki

Isao Kachidoki ( Kachidoki Isao) is a character in the Yu-Gi-Oh! ARC-V anime. He is participant in the "Junior Youth" class of the Maiami Championship and is the ace of the Ryozanpaku School.

Personality
As a child, Isao seems timid and like child his age, Dueling because he thought it's fun, and was initially seemed reluctant to join Ryozanpaku whose Dueling believing is absolute victory. However, the harsh training he received at Ryozanpaku for years has completely changed him into a very violent person, repeatedly physically assaulting his opponent during Action Duels to prevent them from getting cards in order to win at any cost. Like other Ryozanpaku Duelists, he thinks that Dueling is a serious battle and not for fun as Yūya believes to be.

Past
As a child, Isao was given a Duel Disk by his parents and was admitted into Ryozanpaku Duel School. One day, on the day he departed to the school, he was seen walking with Ryōzan Gōdagawa, until he stopped and noticed a young Yūya Sakaki Dueling with his father, Yūshō Sakaki. Seeing them having fun in their Duel caused him to smile, but his teacher told him not to think of Dueling as fun, as the path he was about to walk would be pitch black and full of darkness. At one point in his life Isao had gotten second place in the previous Maiami Junior Youth Championship. According to Nico Smiley, Isao further evolved from the previous tournament by learning Fusion Summon.

Round 1
During his Duel with Yaiba Tōdō, Isao brutally beat up Yaiba in order to prevent him from getting any Action Cards, thus resulting in Yaiba's defeat in an One Turn Kill.

Round 2
During his Duel with Yūya, Isao once again tried to prevent his opponent from getting Action Cards through brutal force. While it seemed like Isao would win, Yūya entered The Awakening, which allowed him to Xyz Summon "Dark Rebellion Xyz Dragon" and beat Isao in an One Turn Kill. This Duel exposed Isao's ignorance towards Xyz Monsters as he thought that since they have Ranks, it was implied that their Levels would be 0 and he could activate the effect of "Idaten the Conqueror Victory Star". When Yūya offered to help Isao up after the Duel, he disdainfully rejected it and bowed in shame to his master and the other Ryozanpaku Duelists.

Fusion Dimension Arc
When Yūya, Kaito, Shingo, and Gongenzaka arrived in the Fusion Dimension to save Yuzu from Academia, Dennis told Isao it was his turn now.

Deck
Isao uses a Star Deck focused on Fusion Summoning his ace monster, "Idaten the Conqueror Victory Star". During his Duels he shows a very violent style, physically assaulting his opponents with martial arts to prevent them from getting Action Cards. His core strategy is Fusion Summoning "Idaten", using its effect to reduce the ATK of his opponent's monsters with lower levels to 0, and equipping it with "Magical Star Sword", which can increase the ATK of the equipped monster by sending Magic Cards from the hand to the Graveyard. He then proceeds to gather Action Cards and use this effect to power up "Idaten" to the point where he can perform a One Turn Kill.