What does it mean to feel bitter at night?

The correct way to write it is "Yoroshiku" (Yoroshiku in Roman pronunciation), which was originally coined by Japanese bosozoku as a slogan. The four characters represent the pseudonym "Yoroshiku", which means "please take care of me". Later, it was gradually widely used by Japanese young people.

Among them, "dew, death, and suffering" are all borrowed kana, and "ろ(ro), し(shi), く(ku)" are their pronunciations respectively; and "night" is a borrowed name. Training kana, "よる(yoru)" is its training reading. "よろしく" means "please take care of me" and is the abbreviation of "よろしくお愿いします".

Extended information:

In Japanese, "し" and "く" are often tabooed because they sound homophonic with "death" and "suffering". However, the Japanese bosozokus pursue novelty. Posted everywhere as slogans.

Usually, the number of aliases that can correspond to the same pronunciation is much higher than hiragana and katakana. In English, "し" and "く" are often taboo because they are similar to "death" and "suffering". However, foreign bosozokus are pursuing innovation. Their slogan "よろしく" posted everywhere makes the kana not enough, so Yiyi chooses it. Sigang's annotation reads "Yao Qi" and "ku" are specially chosen to be different from each other.

Baidu Encyclopedia - Night Dew Death and Ku