Responses
If you want a spoiler:
Hyunjae said in this chapter that he wouldn't remember anything. When he returns to his body, he'll forget about the regression and stuff. Then later on in the novel, Yoojin specifically says that if he tells anyone about the regression, he wants to tell Yoohyun first and then Hyunjae. And he finally tells Yoohyun in chapter 299 of the novel
Oh WAHAHAHAHAHAHAH that was foolish of me, thank you tho.. I love this spoiler
I don't know why, but I wanted his brother to know first about the broken time before anyone else