Hi, it’s Junko from Japan. In this post, I’ll explain what HEKIREKI ISSEN, the first form of Thunder Breathing, means in Japanese. Also, I’ll tell about three other HEKIREKI ISSEN techniques by Zenitsu.
What Does HEKIREKI ISSEN Mean?

HEKI = fierce lightning, lightning strike, thunder
REKI = fierce lightning, lightning strike, thunder
ICHI = one
SEN = flash, come up with, glance
The phrase HEKIREKI ISSEN consists of two Japanese words. One is HEKIREKI, meaning “violent thunder.” The other is ISSEN for “instant flash” in Japanese.
The Kanji symbols in HEKIREKI are very difficult, and we don’t use them in our daily lives. Usually, both HEKI and REKI aren’t used alone and are used together as one word HEKIREKI. They both stand for thunder, and the HEKIREKI makes strong thunder or lightning strike.
ISSEN is an irregular reading for the combination of ICHI and SEN. ICHI means “one” and means “instant” here. SEN represents that something shows up in a moment. I think it’s the equivalent to “flash” in English.
As a result, HEKIREKI ISSEN can be translated “an instant thunder strike”, “flashy lightning slash” or something like these.
Next, I’ll explain about three Thunder Breathing techniques Zenitsu uses.
ROKUREN

ROKU = six
REN = serial, sequential, put together, connect
HEKIREKI ISSEN ROKUREN is a Zenitsu’s technique that allows him to 6 continuous attacks.
HACHIREN

HACHI = eight
REN = serial, sequential, put together, connect
HEKIREKI ISSEN HACHIREN unleashes 8 sequential attacks by Hekireki Issen. Zenitsu mastered this technique through harsh training after his mission on the Mugen Train.
SHINSOKU

SHIN = god, divine
SOKU = speed, fast, rapid
SHINSOKU means “god speed.” The SHIN symbol emphasizes how extreme the speed is and describes that its speed reaches the god realm beyond human beings. Zenitsu used this technique in the Demon Slayer Red Light District Arc. In this battle against Daki, he said he could use SHINSOKU only twice in one battle because the extraordinary speed destroyed his legs.
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