夜露死苦

Eye dialect for 宜しく (yoroshiku, “well”). This use grew out of the practices of biker gangs, who would use kanji in creative ways, possibly for the irony, as biker gang members have generally been regarded as low class and uneducated, while knowing how to read and write kanji is generally a mark of education and refinement.

The kanji are ateji (当て字) but have deliberately dark connotations: 夜 (“night”) +‎ 露 (“dew”) +‎ 死 (“death”) +‎ 苦 (“suffering”).

• (Tokyo) よろしく (Nakadaka – )^[1]
• (Tokyo) よろしく (Heiban – )^[1]
• IPA^(key):

夜(よ)露(ろ)死(し)苦(く) • (yoroshiku) 

1. (slang, dated) Alternative spelling of 宜しく (yoroshiku, “well”), the adverbial form of 宜しい (yoroshii, “good”).

In general usage, yoroshiku is used in parting as a request (short for 宜(よろ)しくお願(ねが)いします (yoroshiku onegai shimasu)) that the addressee think well of the speaker. Some sub-cultures have taken to using the term as a greeting instead. The 夜露死苦 spelling as used by such sub-cultures would thus be a greeting, similar to good morning.