Iselus

Iselus El-Arde Corwen (also translated as Itherus by Sentai Filmworks) is Rayneshia's younger brother and is the primary candidate to succeed Duke Serjiad Corwen, although his father Feynail currently serves as his guardian.

He was first introduced in the Log Horizon TRPG supplementary material, but made an official appearance in volume 10.

Prior to the Catastrophe
Like his sisters Risselthea and Rayneshia, Iselus is the child of Feynail and Sarariya, and thus the grandson of Duke Serjiad Corwen. Because Serjiad himself has no sons, Iselus will inherit his place in the League of Freedom Cities Eastal, despite being a little less than eight years younger than Rayneshia and much younger than Risselthea (who married a knight and was thus denied from inheritance).

Return of the Goblin King arc
Although Iselus is not seen in this arc, he was aware of the Adventurers' help in defeating the main Goblin forces and began idolizing them after that.

Homesteading the Noosphere arc
After Isaac and the Black Sword Knights are sent to Maihama to help improve relations with Eastal, Iselus quickly gains a liking towards Isaac and pursues him everywhere, to the man's annoyance. However, Isaac quickly comes to realize, after being assigned to protect him, that he was much more mature than he looked, as he was seen making plans to improve Maihama despite his young age.

Trivia

 * Iselus shares his voice actress, Mariya Ise, with his sister.