I've asked this question directly to my friends; it's also very common amongst Koreans, but strangely uncommon for the Japanese to do so. Some names simply don't survive moving between languages. A Chinese name for example may be too difficult or strange to use around English-speaking people. Also, an attempt by an English speaker may ruin the tones and even change the meaning of the name (this happened to a Chinese friend - bad pronunciation of her name by non-Chinese gave her name a negative meaning. She quickly adopted a more European name). The other reason is it's more comfortable to adopt a name from your second language so it doesn't feel like you're code-switching. I've also adopted an individual name in Chinese with its own meaning (instead of transliterating my name) - you'll often find westerners who learn Chinese do this.

I think ，they use English name just wanna foreign friends can know they easily。Or maybe just think is interesting。 THANK YOU

to catch up with the the progress of the power of english . or as they just love that . also maybe they want feel the english persons that they are talking with any distance between them and they are lovely and loving their culuter so they take names from them. maybe at all it`s feshion .