Zenitsu Agatsuma

Agatsuma Zenitsu (我妻 善逸, あがつま ぜんいつ) is a member of the Demon Killing Corps and a traveling companion of Kamado Tanjirou.

Appearance
Zenitsu has short blond hair which was originally black, and brown eyes with thick eyebrows. He wears the standard Demon hunter uniform with a yellow Haori with a white triangle pattern on top.

Personality
Zenitsu is a coward and is constantly claiming he doesn't have long to live due to the dangerous job of being a Demon Hunter. He is also a bit of a womanizer and likes to hit on girls who he thinks are cute and ask them to marry him much to their annoyance.

Zenitsu has low self-esteem but still wanted to live up to the expectations others set up for him, but was constantly afraid and would always cry and run away. He claims he wants to live a modest life where he can be useful to someone.

Natural Abilities
Enhanced Sense of Hearing: Zenitsu has a heightened sense of hearing, allowing him to detect danger from even the faintest of sounds.

Unconscious Combat: Zenitsu becomes stronger when he sleeps. When his life is in danger, the fear he experiences exceeds his own limits making him fall unconscious. When Zenitsu is asleep he is able to perform his swordsmanship at a high level purely based on instinct alone.

Swordsmanship
Breath of Thunder Style: Taught to Zenitsu by a former Pillar, Shihan, whom he refers to as Jii-Chan. Shihan once held the title of the the strongest demon hunter. This technique increases the user's strength and agility to equal a demon's. There are a total of six styles that can be used with the Breath of Thunder, but Zenitsu has so far only been able to learn one of them.
 * 1) First Style: Thunder Clap Flash - The user dashes forward and slashes at their opponent with incredible speed. Zenitsu has honed this ability to the extent of being able repeat the dash multiple times in quick succession. So far he has been able to dash 6 times in 1 use of the technique.

Trivia
我妻 (あがつま) can literally mean my wife. There are a few readings for this kanji name, and one of them can be read as "Gasai", such as the name of Gasai Yuno from the manga Mirai Nikki.

善逸 (ぜんいつ) can mean goodness.

In a twitcasting broadcast segment for Kimetsu no Yaiba, Gotouge said that his name was pronounced as [Zenitsu→] with a more dragged out "suu" syllable instead of a strong emphasis on "zen" [Zen↑itsu].