I think for me it has a proper ending. The last few line said at the last episode actually answers most of the questions( At least that's what I think) . Moonsung and all the other team member were lab guinipig. And that's why except moonsung and taesoo everyone had to die. And since moonsung and taesoo are sort of immortal they got to live. But due to the heavy trauma of the incident moonsung had forgotten his 18 years worth life. This is still a mystery like what happened to him during those years. But since it wasn't something important much that's why the author nim left this part I guess. But yeah at the end we see he starts to live a normal life with hoyeon and the revenge part is also complete. The story could have been longer. But yeah this much is still good. 10/10 for me.
I think for me it has a proper ending. The last few line said at the last episode actually answers most of the questions( At least that's what I think) . Moonsung and all the other team member were lab guinipig. And that's why except moonsung and taesoo everyone had to die. And since moonsung and taesoo are sort of immortal they got to live. But due to the heavy trauma of the incident moonsung had forgotten his 18 years worth life. This is still a mystery like what happened to him during those years. But since it wasn't something important much that's why the author nim left this part I guess. But yeah at the end we see he starts to live a normal life with hoyeon and the revenge part is also complete. The story could have been longer. But yeah this much is still good. 10/10 for me.