珍：江戸時代の日本の留学生は、ヨーロッパでもマゲを結っていますね。
佐々木：そうですね。帰国した時のことを考えると、マゲを切るのはよほどの決断を必要としたのでしょうね。
Ketsudan
(Chuugoku no ryuugakusei to)
Chin: Edo jidai no Nikon no ryuugakusei wa, Yooroppa de mo mage wo yutte imasu ne.
Sasaki: Soo desu ne. Kikoku shita toki no koto wo kangaeru to, mage wo kiru no wa yohodo no ketsudan wo hitsuyoo to shita no deshoo ne.
(Talking to a Chinese student)
Chin: In the Edo period when the Japanese went abroad to study, even if they went to Europe, they used to keep their hair in the samurai mage fashion, huh?
Sasaki: That's right. I suppose knowing that they would be returning to Japan must have made the decision to cut their long hair extremely difficult.
Ketsudan suru means to determine, resolve or decide to do something.
I recently had a discussion with Chin-san, a foreign student of mine, about Japanese people who went to study in the West at the end of the Edo period (1603-1867). He was commenting on how the Japanese had tried to learn so many things from the West, but he also wondered what it must have meant for them to stop wearing kimonos and start wearing Western clothes.
I told him that in Japan at that time, kimonos, like the samurai style of wearing their hair in a mage, were a sign of one's social rank or status, and that the deci- sion to give up wearing them was a way of showing their refusal to be bound and tied by the constraints of rank and status. At that time hi the West, distinctions between classes were being broken down, and wearing a kimono with a sword at your side was seen as a sign of your attachment to an outmoded sense of class consciousness.
Of course, walking around London in a kimono and mage would have made them stand out. So when it came to switching from kimonos to Western clothes, Omoikitta ketsudan wo suru hitsuyoo ga atta (They had to make a strongly resolved decision).
That is why they wore Western-style clothes. However, if they cut their hair short, they would not have been able to tie itup in a mage again, and this was something which, Ikura kangaete mo, totemo ketsudan dekinai (However hard they thought about it, thev couldn't bring themselves to do it). Instead they compromised by wearing their hair long until they came back to Japan where they would tie itup in a mage again. Very clever of them, I think.
To give a few more examples of the way this expression is used, you might hear people say, Ima koso ketsudan sum tciki desu (Now more than ever is the time to decide); or to someone else you might say, Yoku ketsudan shite kudasaimashita (Thank you for coming to a decision on this); or again, someone might advise the company president, Shachoo ga ketsudan shite kudasareba, minna yorokobimasu yo (If you give the word, everyone will be pleased). And there are many other situations in which it can be used.