The Great Wave of the Astral World

In volume 34, Femto accomplishes a key part of the God Hand's plans when he splits Ganishka open, provoking a huge explosion that unleashes a giant wave of light that washes over the whole world. The result is a new world called Fantasia, a fusion of the astral and corporeal worlds. 

In episode 308, Schierke refers to it as a "wind" (風 in between quotation marks) for lack of a better word. But in volume 39 (episode 344), we learn what the Great Gurus of Skellig have been calling it: 大幽界嘯 (DAI YUU KAI SHOU).

In the official release, Dark Horse has translated it as the "Great Roar of the Astral World", but that's not a very good translation. The problematic kanji is 嘯 (SHOU), which they translated as "roar". Now, if you check that kanji by itself in an online Japanese to English dictionary, you will indeed get a meaning of "roar, howl, recite emotionally, feign indifference". However that isn't the actual meaning of the word. Unfortunately, such dictionaries aren't without their own limits or errors, as any bilingual person can attest.

The specific meaning of 嘯 is rather associated with exhaling (breathing out) strongly. It's only by extension that it can refer to a tiger's roar, and it's not how a "roar" is actually conveyed in Japanese (it would be 咆哮). It could also be used to refer to "the earth breathing out" figuratively during an earthquake.

This true meaning of a "great exhalation" is why we originally translated it as the "Great Blast of the Astral World" on skullknight.net, in reference to a wind blast. After all, Schierke does initially refer to it as a kind of "wind", and more importantly, it's never shown making any particular sound... Rather it's a wave of light that covers the world.

Which brings me to the true meaning of the word here. Expressions composed of four kanji are a specific feature of the Chinese writing system. In that context, considering each kanji individually is a mistake. To the point, what Miura did here is a play on words between 幽界 (YUUKAI), which means "Astral World" in Berserk, and 海嘯 (KAISHOU), which means "tidal wave". In Japanese, that word is considered obsolete as 津波 (TSUNAMI) is preferred. But it is still valid, and especially so in the context of a four kanji word. What Miura did is replace the kanji for "sea" (海), pronounced KAI here, by 幽界 (YUUKAI).

So a better translation of the phrase is the "Great Wave of the Astral World". This makes complete sense when you consider the visuals on the page, as it is literally a giant wave that washes over the corporeal world. And it also fits with the classic motif of associating the Astral World with water in Berserk, whether in the Black Swordsman arc when we learn about the ocean of souls (and the vortex in it), during the Eclipse where beherits are depicted as droplets rising from the depths of the astral world and referred to as "drops of primed water leading to another world", or in volume 24 when Schierke compares the Interstice to a shoreline where land and sea meet.

One thing worth noting is that when 幽界 was first introduced in volume 24, Miura specified its pronunciation using furigana as かくりよ (KAKURIYO). But to make the pun work in this four kanji phrase, he used the standard pronunciation ゆうかい (YUUKAI) instead. This is proof that he meant to convey this specific meaning.

Lastly, the meaning of a tidal wave evokes the sea invading the land to catastrophic results, which is, again, exactly what happened: the Astral World (sea) rushed forth and washed over the Corporeal World (land). So while there's no way to convey all the nuances of the original, there's no doubt that the best possible translation for it in English is "Great Wave of the Astral World".