Shin’s internal monologue is his last wish. He knows that he has to let Eun Tak pull out the sword so that she can survive and he’s accepting that here. What he’s doing is making the wish that he and Eun Tak are reborn together so that he can love her again [and confess to her then that she is his first love].
One day after 100 years
When the weather is good
enough
I wish I could tell her
that she was my first love
To spend a lifetime with Eun Tak, Shin was hoping earlier in the episode to spend 80 more years alive as a Goblin [a rough estimate of the years left in Eun Tak's lifetime. Even if it means dealing with constant pain from the sword, that's what he wants; a lifetime with her. But here's the problem....
ET’s birthmark is fading; she’s losing her purpose in life because Shin isn’t letting her pull out the sword. There’s a time limit to how long Shin can keep prolonging the sword being removed.
Once the birthmark fades, time is up.
Eun Tak is 19 years old right now. The average human lifespan is ~100 years, give or take a few. If we factor in that there may be a waiting period between the time of death and time of rebirth, 100 years would also be a rough estimate of the time Eun Tak herself would be reborn in her next life. So what Shin is asking is to be reborn with her. He wants to meet her again in his next life and he wants her to be his first love again in his next life. He wants to be able to tell her what he thinks he cannot/should not tell her now; She is his first love.
Shin accepting his death here also parallels the way the Queen had to accept her death in Joseon times.
Like Shin, the Queen had to accept that she would have to die to protect someone she loves.
Like Shin, the Queen had to accept that she would die AT the hands of someone she loves.
To me, this is the true punishment; not his 900 year stint as a Goblin.
Shin needs to feel what the Queen was feeling at the time of her death. He needs to feel exactly what it’s like to not only die at the hands of someone he loves, but to resign himself to the fact that he HAS to die at the hands of someone he loves, in order to save that person. And it must be at the time when he most wants to live.
The moment the Queen was shot is what I suspect to be the moment she most wanted to live. She wanted the King to choose to save her, but instead he chose to kill her.
Thoughts on the Future Sequence:
So far we know that Shin can see into someone’s future, but we don’t know exactly how far. What if the vision he sees of Eun Tak at 29 isn’t the Eun Tak in this life, but ET in her next life?
Shin tells us that sometimes people are born with the same face. It could be that ET is born with the same face in her next life and she happens to come across the same waiter [also in his next life but not necessarily the same face]. It could be that the Deity was trying to show him that even if he has to give up his happiness with her in this life, there is still the possibility of meeting her in the next.
Our happy ending may not be a happy ending in this life, but in the
next.