Isaac is described as having "a head full of blood-red hair and a confident, contemptuous smile on his face." He is rather tall, almost equaling Krusty in height.
Isaac is a rowdy person who enjoys fighting, taking comments from his guild members like "You're really naggy, Commander," and "Chief is an idiot" in stride and treating them like compliments. Though he is easily irritated when people don't immediately agree with his views, he is not unwilling to listen to others.
Early on, Isaac is antagonistic, elitist, and proud. Even before the Catastrophe, his arguments with Woodstock W over his elitist policies culminated in Woodstock leaving the guild, and Marielle wonders if "he just enjoys excluding others." He regarded People of the Earth as NPCs with no minds of their own and bought EXP Pots from Hamelin despite knowing the guild's cruel methods.
He grows out of this unbecoming side of himself after the Round Table Alliance is established, and reveals that his gruff demeanor hides a thoughtful side. His aggressive policies in the aftermath of the Catastrophe were meant to keep his guild members motivated and distracted from the uncertainties of their current situation. Despite his negative initial impression of Iselus, he quickly came to respect how hard Iselus worked to become a suitable successor to his grandfather. He appears to respect those who accomplish things through their own effort, and strongly disapproves of Eins' more communistic approach to Akiban affairs.
Although Isaac is normally hot-blooded and easily agitated, he is methodical and calculating in battle.
Before the Catastrophe
Isaac was a carpenter. Although he's had a couple of girlfriends in the past, the relationships always ended shortly thereafter.
He invited Shiroe to join his guild a few months after Debauchery Tea Party was disbanded but got turned down. After forming the Round Table Alliance, he realized that he only understood the surface of Shiroe's personality.
Isaac rallies his guild, preparing to embark to train themselves for battle in the alternate world.
Round Table Conference arc
When Marielle and Shiroe discuss the situation in Akiba, Marielle tells him that the Black Sword Knights and the Silver Swords are aiming for level 91. Marielle holds a rather low opinion of him, stating that "the Black Sword Knights always have a thing for being the best," and derides his strict requirements for recruiting new members. Shiroe comments that Isaac is trying to compete with the D.D.D, which simply absorbed smaller guilds, by using "quality over quantity." However, this presented another problem—they would have to fight monsters level 85 or above, which is difficult after the Catastrophe.
This brings the two to the main issue at hand: the guild's usage of EXP Pots, acquired from Hamelin through the latter guild's abuse and usage of low-level players that they tricked into joining. This leads to Shiroe's determination to both better the city and destroy Hamelin.
Isaac quickly learns about the Crescent Burger, the first prepared food with flavor known since the Catastrophe, and later receives an invitation to attend the Round Table Conference. He comments to Rezarick that he is interested in the meeting solely because Shiroe had a hand in the operation.Isaac and the other guild masters meet at the Guild Meeting Hall to attend the Round Table Conference. When Shiroe begins to introduce himself, Isaac interrupts him, identifying him as "Shiroe of Debauchery" and telling him that everyone knew his name. After William's departure, Isaac and Krusty question Shiroe's ability to affect change in Akiba. After Shiroe reveals that the Guild Meeting Hall is under his control and with it, every guild's ability to use its services, Isaac grows hostile. He calms down after Calasin, Michitaka, and Roderick reveal the development of a steam engine, though he doesn't understand its ramifications until Roderick explains it to him.
Along with the conference's remaining participants, Isaac eventually agrees to the foundation of the Round Table Alliance. When Log Horizon moves into their new guild building, Isaac pays a visit with some of his Summoners. Under the pretense of combat training, they summon Undines to flood the first two floors, cleaning it in the process. After they leave, Nyanta comments that he isn't such a bad person, and Shiroe decides that this was Isaac's way of making up for his behavior at the conference.
Summer Trainning arc
When the Round Table Council meets to discuss Eastal's invitation, he suggests that a member of the Production Guilds attend. At Isaac and Soujiro's suggestion, the three Production Guild masters settle it through rock-paper-scissors—much to Michitaka, the loser's, ire.
Return of the Goblin King arc
During the Return of the Goblin King event, Isaac and his guild were dispatched to Susukino to help evacuate any Adventurers who wished to leave the city, instead of assisting in the Goblin and Sahuagin suppression.
Libra Festival Arc
During the Libra Festival, the Black Sword Knights and D.D.D took charge of border patrol, checking on incoming carriages and contents and making sure that everything ran smoothly. Isaac sits in the middle of the Black Sword Knights' tent, giving orders to his men and taking their reports. While he mentally congratulates himself for being a good leader, Krusty comes to check up on him. Isaac reminisces on the Debauchery Tea Party rise and fall, and on his failed attempt to recruit Shiroe. After Krusty gets him to understand Shiroe more, Isaac decides to take a walk around the city since just sitting there was getting boring.
When Shiroe realizes that someone was trying to sabotage the festival, he orders Isaac to have his men quell any fights that were turning violent. Later, he is assigned to security detail during Raynesia's dinner party.
Route 43 arc
Isaac attends a Round Table meeting to discuss the current situation within Akiba: the increasing lack of motivation among some Adventurers as well as the rise in wealth gap. Several proposals were exchanged but no verdict was reached.
As part of Shiroe's plan to improve relations between Akiba and Maihama, the Black Sword Knights were sent to Maihama to train its knight order, the Glass Greaves. Slightly misunderstanding his objective, however, he ends up trying to power level them, though the Glass Greaves didn't mind. During his meeting with Shiroe and Calasin, he mocks Calasin as a "lolicon" due to the latter's interest in Minori's abilities, and displays his annoyance at Rezarick for calling him "Isaac-kun" (Isaac the Young).
In Maihama, Isaac finds himself bored of training the Earthling knights, although he commends their determination and their willingness to keep up with his rigorous training. While he takes a break under a tree, Iselus, Rayneshia's younger brother, finds him and begins bugging him. Rezarick soon joins them, and further compounds Isaac's frustration by teaching Icelus to call the guild master "Isaac-kun." With that, Isaac decides to go back to training the knights.
Sometime later he was asked by Serijad Cowen to keep a close guard on Iselus in preparation for the young childs birthday as well as the announcement he would be the family, tough finding it a pain he agreed to it.
He later attended the party and thwarted an assassination attempt on the boys life by People of the Earth assassins from Westlande.
Collapse of the Round Table arc
Nightingale's Song arc
Isaac vs. William Massachusetts
After training with other members of the Black Sword Knights, Isaac prepares to leave when his horse was startled by an arrow. Realizing who was there, he taunts William Massachusetts by repeating "Round Table Alliance, Round Table Alliance," aware that this was why the other battle guild master had approached him.
Soujiro meets up with Krusty, Isaac, and Michitaka, since the three battle guild leaders were having their weapons repaired by Michitaka. Isaac greets Soujiro as "West Wind" and adds that it was unavoidable to encounter enemies. After the meeting, Soujiro is leaving with Isaac when two members of the Black Sword Knights approach them, telling Isaac that they were there to escort him. After waving off the two members, Isaac suggests having his guild merge with Soujiro's due to the uncertainty of the world around them. Although Soujiro disagrees with Isaac's view of the world, the two members cut in to try and persuade Soujiro otherwise—although not in the way that Isaac would like, as their primary concern was the lack of women in the guild. After Soujiro reiterates his decision not to take up Isaac's offer, Isaac leaves after reminding Soujiro that this made them enemies. After Soujiro's brief run-in with Magus, Magus meets up with Isaac in a cave to deliver EXP Pots.
He is mentioned in the meeting between Marielle, Akaneya Ichimonjinosuke, Woodstock W, and Soujiro after Hamelin and Magus are brought up. It turns out that Woodstock had already gone to Isaac to try and dissuade him from using the EXP Pots. As Woodstock had expected, the discussion turned sour and Isaac refused to budge on his position. Woodstock bemoans that the guild hadn't changed at all since he had left, which was before the Catastrophe.
When Soujiro announces his plan to kill the PKers, Woodstock goes to confront Isaac again. Irritated that Woodstock had come back, Isaac reminds Woodstock that the latter always demanded things from others when he couldn't do it himself. In the process, Isaac reveals his motivation for having the guild aim to surpass level 90 - he saw it as the best course of action for his guild members, to divert them from the boredom of their current world. Once Woodstock mentions the EXP Pots, he initially defends the usage of in-game items before learning that Hamelin was abusing the younger members whom the EXP Pots were coming from. Although fazed for a second, he resumes defending himself, but Woodstock questions whether Isaac was really okay with Hamelin's actions. At that moment, Soujiro arrives to point out that Isaac really did feel guilty about what he was doing, that he was nice guy who was "just a little shy," and that he cared about Akiba despite putting the guild first in his priorities. Soujiro's constant pestering causes Isaac to snap and he tries to attack Soujiro, who simply dodges it. He finally relents and decides to make their PK-hunting quick, only to yell at Woodstock again because the latter was not coming along.
When the PKers are driven into a dead-end by the West Wind Brigade, Soujiro and Isaac show up to kill them, with Isaac calling them pathetic for resorting to Player Killing. When some of them decide to attack Isaac first, he mocks them for their decision before revealing his sword's special ability, which forced his opponents to focus on him. He then easily slaughters them as Soujiro takes out the rest. Afterwards, he tells Soujiro that he wouldn't help him anymore, but would hunt any PKers that wandered into his guild's hunting grounds, and points at Magus while telling Souji that he would continue buying EXP Pots. He then leaves, allowing Soujiro to confront Magus alone.
- Out of approximately 40 characters, Isaac came in 18th place. He rose to 6th place out of 86 in the second popularity poll.
- ↑ 1.0 1.1 1.2 Log Horizon Anime: Episode 9, Round Table Conference
- ↑ Twitter. Log Horizon TRPG. Isaac's birthday.
- ↑ Mamare Touno's third Q&A session on 4chan, 23 March 2014
- ↑ https://twitter.com/loghorizon_TRPG/status/583068634920046592
- ↑ Log Horizon Drama CD: Black Sword vs. Berserker
- ↑ Log Horizon web novel: Chapter 85
- ↑ Log Horizon Light Novel: Volume 5, Chapter 3
- ↑ Log Horizon Anime: Episode 7, Crescent Moon
- ↑ Log Horizon Anime: Episode 8, Villain in Glasses
- ↑ Log Horizon light novel: Volume 2, Chapter 4
- ↑ Log Horizon light novel: Volume 2, Chapter 5
- ↑ Log Horizon Episode 10, Grab it in Your Hand
- ↑ Log Horizon Episode 11, An Invitation From Eastal
- ↑ Log Horizon's 2nd Official Popularity Poll Results
|Round Table Alliance|
|Guilds||D.D.D • Black Sword Knights • Honesty • West Wind Brigade • Marine Organization • The Roderick Firm • Shopping District 8 • Crescent Moon Alliance • Grandeur • Radio Market • Log Horizon|
|Representatives||Krusty • Isaac • Eins • Soujiro Seta • Michitaka • Roderick • Charasin • Marielle • Woodstock W • Akaneya Ichimonjinosuke • Shiroe|
|Black Sword Knights|