Another Crazy with a H

It's a romantic story about the couple, nothing about the creature. Overall it's bad and the storyline doesn't make sense. I'm glad its not more than 7 episodes. A couple of things that doesn't make sense: ((1))Master Jang was injured and crawled towards a water tank. Chae-Ok watched him crawled and dropped into the water tank. After Jang dropped into the water, he looked at Chae-Ok. It's ridiculous! Both of them were on the same floor, looking at each other, and after he dropped into the water, he can still look at her from inside the water tank!! ((2))The look of the creature didn't change/upgrade for 79 years! After decades of experimenting, shouldn't the bad guys have invented something new? Drinking a glass of water with Najin which is the same as the olden days, why! How is there no progress on the experiment in the modern world. ((3))Chae-Ok and Master Jang didn't have the weird "tentacles" but Seung-Jo have it at his hand. During Chae-Ok's flashback, she's in a daze and upset that she killed all the people. She looked around at the dead people and their eyes gone so it showed that she used the "tentacles" to kill. While fighting all those bad guys in present day, why doesn't she and Jang uses it to fight them? Why all the unneccessary fighting action when they supposed to have the superpower from Najin? If both of them have the weird "tentacles" and don't want to use it on humans, then why didn't Jang use it when he fights the creature? What exactly does the Najin do in the body beside maintaining youth, scars, powerful punches and revived you from death? ((4))The young boy with polio killed the people at the train station cause of the need to feed Najin but why this didn't happen to Jang and Chae-Ok. The plot says the Najin needs to feed after recovering and why Jang & Chae-Ok doesn't seem to need to feed their Najin? There's one scene of Chae-Ok struggling with the need to feed and inject herself with something. The other scene was the flashback of Chae-Ok when she first had Najin in her. There's a scene of her telling Jang to leave her alone or she might have to kill (feed on him) him, then Jang hugs her and she doesn't need to feed anymore. Wow! ((5))What is "Kuroko"? A bunch of them look like killers and when you hear the weird sounds they made, they don't sound like human. If they are non-human, they probably should be tough but they get killed and beaten up pretty quickly. ((6)) Najin is out of Jang and Chae-Ok's body and thry still look like they were before? Shouldn't the body grow old and age fast when Najin is not in the body anymore? I supposed Najin is maintaining the body and if Najin leaves the body, the body should deteriorate. ((7))Why Najin didn't turn all the human into the ugly creature like Chae-Ok's mom or other creatures we see in season 2. Master Jang, Chae-Ok, Seung-Jo, Lady Maeda looks fantastic, so how does Najin affect the body?