Just a little addition, @WEnchanteur, to your wall of text earlier.

Re. that 54:26 mark when TU entered Sato’s office

He overheard Fukuda reporting that the Gugukdan was behind the attack and asking, “Could she be one of them, too?”

He assumed that they were talking about GG, and he was worried about her, when in fact Fukuda and Sato were talking about SoRan’s possible involvement in the bombing.

I don’t think SoRan entered TU’s mind.

I agree with you, @WEnchanteur. Even before TU showed up at PY’s residence, he’d already figured out that SoRan was involved in the attack because of the pearl earring. He was listening behind the door when Fukuda ordered the military troops to search all female guests’ houses. He then remembered noticing SoRan’s missing earring. That’s why he suddenly volunteered to join the house check.

I could see two reasons:

a. To arrest SoRan. He told the police that presence there was for protocol: he wanted to avoid an diplomatic issue. However, part of me would like to think that he also wanted to ensure that, if she was arrested, she wouldn’t be tortured like the other Gugukdam (wait, SoRan’s ex wasn’t a Gugukdam member).

b. To ascertain the whereabouts of GG. He was distressed to see her leave him and wanted to make sure that she had returned to the residence.

Upon arrival at PY’s residence, the police demanded to see the missing earring. TU knew SoRan was lying when she said it was in her drawer. But as the police were about to open the drawer, TU volunteered (again!) to look for it himself.

It seemed to me that he was delaying the inevitable arrest. He could’ve just allowed the police to search for the earring himself. BUT he stepped in again. Interesting, right? To me, if TU didn’t have an ounce of sympathy for Gugukdam and the cause of the pro-independence fighters, then he wouldn’t have interfered.

He gave PY the LOOK, a stern, forbidding look that seemed to say, “I know what you did.”

Meanwhile, SoRan got her gun ready. She was just rarin’ to shoot him as retaliation for the cook’s death.

The way I see it, TU had two options after opening the drawing. Obviously, the earring wouldn’t be there so TU would have to either:

a. Order the police to arrest SoRan. This would have a domino effect: SoRan would shoot him at point-blank and the police would fire on her and PY. Body count: all three Koreans.

or

b. Cover up for SoRan. He could lie that the ring was there, then quickly shut the drawer before the police come forward to take a look for themselves. His word would be enough.

But just like the Japanese female personnel stopped the bomb assassination of her bosses at the last minute, GG also stopped the would-be bloodbath in SoRan’s bedroom. GG spared TU from making a hard decision when she burst into the house.

Note: I like how visuals and sound her shoes made as she sprinted up the stairs. It made great contrast to the slow-mo when TU was about to open the drawer, the stillness in the room, and the close-up on the confused faces. She made her entrance intentionally loud and noisy to stop the impending doom.

While GG fully expected the police to be there (she must have seen the vehicle outside), she wasn’t expecting to see TU, too. Hence, the question in her head, “Are you here to arrest us?”

And she “please-d” their way out of the trouble.

Later, when TU returned to his home and replayed the events of the night, he realized that GG was in on the bomb plot. He understood now why she grabbed his hand and ran away with him before the bomb exploded.

The following morning, he dropped in on his father’s office for two reasons:

a. to deliver a fresh change of clothes, like a dutiful son, and
b. to check what his father knows. To me, he’s become a de facto spy, too, at this point.

Meanwhile, his adoptive father made some conclusions of his own, too. He was long suspicious of Geum SoHee (aka GG) because of her last name. Then, he began suspecting his own adoptive son Hideo/TU because of the bloodstain on the photo ID of Mr. Geum. And now, he suspected that PY’s wife, SoRan, was a Gugukdam member because of the earring.

Noteworthy: Though he disclosed his suspicions about Geum SoHee and SoRan to Fukuda. But his suspicions about his son? He kept that to himself.

TU: Your wound is pretty deep. Shouldn’t you get it check at the hospital?
Sato: Don’t worry. There’s no shortage of people who want me dead. But I’m not going to die.

TU bowed. He began packing away his father’s used clothes. He noticed the news report on his father’s desk, and then the gun. His hand faltered. Sato, who was observing him through the mirror, saw that hesitation.

My comments:

a. To me, the men had two different thoughts running in their minds when they look at the gun. For TU, he remembered what his father had just done the previous night. He shot two men with that gun.

b. For Sato, however, he was wondering and waiting to see whether TU would pick up the gun and aim it at him. The previous night, after he shot the elevator kid and cook, he told TU that he was done going easy on him. He told him to remember, “You’re nobody if I’m dead.”

But if TU had aided the Gugukdam in their attempt to kill him, then it was clear to Sato that TU didn’t care if he died and, consequently, lost his social status and privileges as his son.

c. I think the use of the mirror signaled a change in Sato’s approach with his son, TU/Hideo. TU/Hideo is now going to be under his surveillance. Sato was going to watch his every move because he no longer trusted him.

d. Additionally, the use of mirror indicated to me that there was now a barrier in how Sato viewed his son. He wasn’t looking at him directly, face-to-face. Instead, he was looking at him literally through another medium. This implied that his vision of TU/Hideo could become distorted at any point.

e. Note: the camera trick used here is called a “rack focus.” It’s when a camera sharply focuses on one object, then blurs it and then focuses sharply on another object either in the foreground (or background).  This is usually done to highlight a change or expose a new “threat” that was first hidden from view. In this case, it was Sato’s watchful eyes on TU/Hideo.

f. Lastly, TU must now watch his back since Sato no longer trusted him.

TU: I acted rashly yesterday. I shouldn’t have let my feelings get the better of me. Forgive me.
Sato: Should I be glad you’ve finally realized it?
TU: (bowing) I’m sorry. Apart from finding out that the Gugukdam did it, did you find anything else?
Sato: Why do you want to know?
TU: I’m worried about you, Father. Yesterday’s attack was serious.
Sato: (smiling a little) Focus on the foreign press and prepare for the League of Nations’ visit. That’s what you need to worry about, nothing else, Interpreter Sato.
TU: Yes, understood.

My comments:

a. The problem with these men is that they’re better at deception that GG and SoRan are. With TU’s ready answer, I can’t tell whether TU is truly worried about his father or is only playing a dutiful son and is really trying to get info from him about GG’s situation.

b. As for Sato, I’m not sure if he smiled because he’s pleased at TU’s concern or he’s being cynical.

c. Whatever it is, the two men have their guards up moving forward.