May 9
[Chapter 232 spoilers]
The fact that Sung Hyunjae as Sigma isn't the Hyunjae Yoojin knows but Yuhyun is still himself made me think that possibly, just like with how Hyunjae's pre-regression self took over the current Hyunjae's body, right now the real Hyunjae is also stuck inside Sigma's mind and unable to do anything while Sigma is still his usual self.
Considering that the current Sung Hyunjae rejected the merge between him and his pre-regression self, it's plausible to assume that Sigma rejected our Hyunjae too. Talk about being so contradictory that you contradict your very existence too lmao