Not explictly shown, but around 32:30 the mc (Lee Hae-sook) is kneeling on the ground and looks over to see her hand has landed on the end of her cat Sonya's tail. We only see about half of the tail, but the implication is that the cat lied down there on the ground and passed away, likely from natural causes.
(around 21:50-22:12)
In a flashback, we see the day MC Lee Hae-sook gained custody of Lee Young-ae, her protoge. In exchange for clearing his debts, Young-ae's father signs a contract to hand her over to Hae-sook. A younger (around 8 years old, if I had to guess) Young-ae is shown sitting on the ground eating some taiyaki, her nose bloody, implying that her father beat her in some way. Once the contract is signed, Young-ae smiles at Hae-sook, clearly happy to be staying with her instead.
At the Heaven checkpoint, where souls need to leave behind anything they might be clinging to, we see a soul who was a firefighter, clinging to an oxygen mask, insisting he must hold on to it. In a flashback, it's shown he was trapped in the stairwell of a burning building with a young girl, keeping the oxygen mask on her face for her. As he radios his location to his collegues, he states they have about 5 minutes of oxygen left, while coughing and wheezing. He eventually succumbs to smoke inhalation, though we see the little girl try to put the mask on his face in an attempt to save him. When the flashback ends, the little girl has appeared at the checkpoint too, meaning she too succumbed to the smoke off-screen.
There are themes of converting to Christianity (no explict converting), debating if one can use the cross for a gravestone as a non-believer, and people are shown/heard praying to the Christian god.
The character of Young-ae knocks herself out with a frying pan twice. It is meant to be a comedic gag though, as she doesn't want to listen to her adoptive parents being lovey-dovey in the other room.
The MC has a nightmare of ending up in hell, in which she sees zombies/demons crawling up a cliffside to try and grab her. (Timestamp: 22:40 - 23:16)
To get to Heaven, whatever mode of transport you take to get there will stop by Hell first, where the souls who belong there will be compelled to get out at this stop. Out of all the passengers of the subway train our MC takes, we see around half of them being made to walk or fly out of the train, crying out and screaming as they dragged out by an invisible force into the dark mists of Hell, though no typical "demons" are shown here.
(Around 32:30 in the episode)
Main character Lee Hae-sook has a cat, Sonya, who passes away. After having a somewhat harrowing vision in which she sees Sonya attacking the grim reader coming for her paralyzed husband, Hae-sook hurries home. She finds her husband luckily still alive, but Sonya has passed away.
The cat's dead body is not shown, but Hae-sook is shown to take a shuddering breath as she realizes that upon kneeling on the ground, her hand has landed on the end of the cat's tail, suggesting the cat is lying there on the ground near her husband's bed.
The scene then cuts to Hae-sook and her adoptive child/protoge Lee Young-ae having buried Sonya, with Hae-sook putting a little pendant with Sonya's picture on it around the gravestone cross.