After the shogun called for criminals to acquire the Elixir of Life from the dangerous island known as Kotaku, in exchange for a pardon for their past crimes, Genji joined in the expedition team as one of the Yamada Asaemon monitors and was assigned to keep watch over the criminal, Moro Makiya.
Genji was a large, muscular man with dark and white hair and large eyebrows split into three sections. He wore the standard attire of a Asaemon, which was a white robe with a bell tied on the left collar along with a hakama held together with a waist cord that holds his two swords, and sandals. Instead of having the standard sleeve straps, Genji costumed his uniform with chains.
Genji was said to be a man who was only best suited to martial arts and had trouble with other activities. Like a few of his fellow clan members, Genji believes that women in the Yamada clan should not follow the path of a samurai. He stated to Sagiri that he believed that her only duty was to become the bride of the next head of the clan and that her skills were inferior when it came to surviving on the island. However, after understanding how Sagiri chooses to live her life, Genji came to accept her as a samurai and entrusted her to kill Rokurōta with his sword as his last dying wish.
As a samurai, Genji was a very strict man when it came to bushidō. He believed that a samurai's sword contains the wielders soul and felt disappointed after he noticed how Sagiri lost her original sword. He also became enraged with how she spoke her mind about wanting to live her life, stating that what she said was not the way of a samurai.
Despite his serious demeanor and intimating appearance, Genji had a weakness for women, something he was known for by his fellow clansmen. Although he was a slow learner, Genji was determined to write a letter to a women he had feelings for with the help of Shugen teaching him calligraphy that took him a year to learn. Instead of returning home as instructed after his assigned criminal was killed by Yuzuriha, Genji fell for her charms and decided to watch over her while making up the excuse of saying that she was too dangerous to be escorted by one Asaemon.
Genji was also kind and caring as he showed his gratitude to Shugen for helping him learn calligraphy by writing a letter of thanks and reading it out loud in front of the public despite the embarrassing moment. He also gave his little sister words of encouragement about her stature.
Genji became one of the few Asaemons who got assigned to a criminal and sent to search for the Elixir of Life on an island ordered by the shogun.
After arriving on the island, Genji's assigned criminal, Moro Makiya, was baited and killed by Yamada Asaemon Senta's assigned criminal, Yuzuriha. Although he no longer needed to stay on the island anymore, Genji easily fell for her charms and decided to keep watch with Senta. Later, the three encounter Gabimaru and Sagiri battling monsters and lend them their support. Noticing that Yuzuriha has two Asaemon, Sagiri asked why Genji was escorting her, which he replied saying that he found that she was too dangerous to be escorted by a single Asaemon and made the judgement of watching over her. However, Gabimaru and Sagiri saw right through him. After Yuzuriha convinced Gabimaru into pairing up to find the elixir, Sagiri falls unconscious from the toxins spread through the human-faced butterflies.
Once they brought Sagiri to a cave to recuperate, Genji watches over her while the rest contribute to a certain workload. Once Sagiri wakes up, the group start discussing what they discovered on the island. Gabimaru explains how he and Genji found different types of plants and how they are connected to the samurai that were first dispatched. Senta and Sagiri then discuss about the statues and monsters characteristics and decided that they should do further research. Genji approaches Sagiri outside and demands that she return to the mainland, seeing as how her skills were unfit for surviving on the island. Senta overhears their conversation and tells them about the samurai who went missing after departing to the island. However, despite the warning, Genji tells Sagiri to leave at dawn. By nightfall, Genji watches over Yuzuriha.
The next day, Genji is told by Sagiri that she will not be leaving and tries to have him accept the path of a samurai. Feeling angered by her words, Genji draws out his sword and attacks Sagiri but has his sword snatched by her. He then yells at her for this act, only for Sagiri to try to warn him of Rokurōta standing behind him. Genji notices Rokurōta behind him and pushes Sagiri out of the way, resulting in a grievous wounded from his torso by Rokurōta's attack. Sagiri rushes towards his aid while Gabimaru arrives and fights Rokurōta. Genji tells Sagiri to leave him behind but hears her refuse. Genji found it strange how Sagiri was starting to act like a woman compared to how she was talking like a man earlier. Sagiri says that she didn't care if she was acting as either a man or a woman as long as she can help out a comrade. Hearing her words, Genji finally understands how Sagiri views herself and gives her his sword, putting his faith in Sagiri in killing Rokurōta. After Rokurōta sets the whole area on fire, Genji succumbs to his wounds and dies in the fire.
Abilities and Powers
Since he was the 8th ranked Asaemon, Genji was recognized by the Yamada clan as one of its strongest members and a suitable candidate to become the next head.
Befitting his bulk, Genji was known for his unparalleled monstrous strength. As shown by Shugen's ability to imitate his strength, Genji's physical power became great enough to even beat Tamiya Gantetsusai who was physically strong himself.
According to and demonstrated by Shugen, Genji's swordsmanship was complimented by his wrist strength that can cause swordsmen to lose in a clash of swords. Like every Asaemon, Genji was capable of decapitating a person with a single cut of his sword. He was even capable enough to behead a Sōshin with a single cut.
- Genji ranked 38th place in the manga 1st Character Popularity Poll.