Replying...
Intro. MJ went to buy a pregnancy test and when she returns to the park where Jungkook is waiting for her, she shows him the result. The test came back positive. That means MJ is pregnant and both, who are only 17 years old, realize that they are going to face a teenage pregnancy. That's why the atmosphere is so tense: neither of them expected something like this and they still don't know what to do or how to react.

Jeon Jungkook Teen Pregnancy

@MJ