No matter who you are or what your occupation might be, knowing more than one language is always a terrific strength. Some people are born in bilingual households, while others just work really hard to learn more languages. In K-pop, idols often come from a mix of both backgrounds, and there are several groups where at least one person knows how to speak more than just Korean. The group NewJeans in fact has several members who can speak more than just Korean. So among Minji, Hanni, Danielle, Haerin, and Hyein, here is the answer to who in NewJeans speaks English (and other languages, like Vietnamese).
Explaining Who Speaks English, Korean, and Vietnamese Languages in NewJeans
Hanni and Danielle are native English speakers, having been born in Australia. Hanni also speaks basic Vietnamese because her parents are originally from Vietnam, though she does not appear to be fluent. Hanni furthermore speaks fluent Korean, presumably learned during her predebut period as a trainee at ADOR. Meanwhile, Danielle grew up in a bilingual household, as her mother is from South Korea, so she is also a native Korean speaker.
Although Minji is not a native English speaker, she does speak a competent level of English as a result of rigorous studying in school in South Korea. (She also briefly practiced English during a homestay in Canada.) In fact, Minji explained in an English-language interview that, if she had not become an idol, she probably would have studied other languages at university, especially English, because she is interested in the different meanings that come with sound. Since she is inherently interested in other languages, it compelled her to study English harder.
Haerin and Hyein can speak some English but not at a level that has been demonstrated to be fluent. However, they do seem to understand a good amount of English as a result of living with the other NewJeans members, who will casually switch between speaking Korean and English. It is worth noting that all children in South Korea are typically required to study English as part of the school curriculum, though arguably few children develop fluency without additional studies at after-school schools, which are called “hagwons.” Hagwons can be rather costly, so in some cases, the mere ability to speak fluent English could be considered a status symbol in South Korea.
But to summarize, in NewJeans, Hanni and Danielle are native English speakers, while Minji speaks fairly fluent English as a result of studying hard. Everyone in the group speaks fluent Korean, and Hanni speaks some basic Vietnamese as well. As they get older, the members who are not native English speakers are likely to become much more skilled in the language.