koso こそ

In Japanese, koso こそ has various meanings, and it's a rather tricky adverb. Its most common usage is to say whatever precedes it is the suitable, the real, true, or best, compared to others, unsuitable ones, fakes, or unfits. The closest thing is English would be the word "rather."

(not to be confused with kozou 小僧, which means "boy" or "brat." See bocchan for origin.)

It's usually seen in the following two phrases:

• kocchi koso こっちこそ
• kochira koso こちらこそ

Which generally translate to "I'm the one who should be saying it," or "doing it." Because kocchi and kochira can be used to say "I," or "my side," "my party," and so on.

Thus kochira koso is like: compared to you (socchi, sochira), I'm the party more "suitable" to say it in this situation. It makes more sense for me to say it, than for you to say it.

• kochira koso arigatou
  こちらこそありがとう
  My side rather [than your side]: thank you.
  • I'm the one who should be saying arigatou.
  • I should the one doing the thanking.
  • I should be thanking you.
  • No, I thank you.
• kochira koso gomen
  こちらこそごめん
  My side rather [than your side]: sorry.
  • I'm the one who should be saying gomen.
  • I should be the one apologizing.
  • No, it's me who should apologize, not you.

It can also appear in the end of the phrase:

• arigatou
  ありがとう
  Thanks.
• iya iya, kochira koso
  いやいや、こちらこそ
  No, no, my side rather.
  • No, no, I'm the one who should be [thanking you].

This "rather" translation sounds very weird, I know. You might be wondering why we don't just say something like:

• sore wa ore no serifu da
  それは俺のセリフだ
  That's my line.

That's because that sounds kind of rude, like you just said something I was supposed to be saying, you stole my line, and the point of kochira koso is normally to be polite instead.

Some other ways koso used:

• ima koso
  今こそ
  Now rather [than whenever else].
  Now [is the time.]
  • To do something.
  • Not other times—other times are unsuitable—now, this time, right now, is the best, most suitable time, to do whatever we're supposed to be doing.
  • Not yesterday, not tomorrow: right now.
  • ima 今
    Now.
• konkai koso
  今回こそ
  Time time rather [than other times].
  This time [for sure].
  • Previous times didn't work, but this time, for sure, it's going to work. Because this time we've got everything ready, unlike the other times, in which we merely thought we had everything ready, but we didn't, in fact, have everything ready.
  • So this time, for sure, it's going to work, even though other times it didn't.
  • konkai 今回
    This time.
• kare koso
  彼こそ
  He rather [than other people].
  He [is the one who is...]
  • Unlike other people, he, kare, is the one who is the real deal. The one whom you should really call... whatever you're calling other people.
  • You may as well say others are inferior or fakes compared to him. Because he is the real deal.