The actual story follows Natsumi Andō who allegedly experiences heartbreak and commits rail suicide on July 20th at 11:36pm,⁵⁾ so Mona takes her into the afterlife. The two briefly pass 'Heaven', interact with the cheerful AA characters, but Mona properly guides Natsumi to 'Hell' where she finally tosses her pendant away. Much of the animation has already been 'over-analyzed', so here are the translated details:

• 0:07 - The first signpost reads 'death' (死, shi) in a distorted font.
• 0:14 - The alleged 'break-up' scene between the two.
• 0:16 - The boy appears to be leaving, but some have interpreted this scene as a hanging.
• 0:19 -
  • The train station's signpost read 'EAR', likely 'EARTH' given the blue planet behind it.
  • The skeletal fish-themed train implies a trip to the Sanzu River. Some believe it's a reference to 'maguro' (マグロ), the Japanese term for 'tuna' and the slang term for 'corpse'.
  • The shooting star monument. Historically, a 'falling' star was associated with death or disaster.
• 0:21 - The rainbow. The concept of crossing a 'rainbow bridge' is a common euphemism for 'death', describing the trip from the 'land of the living' to the 'land of the deceased', usually for pets.
• 0:32 - The signpost reads 'HASi', which confirms that they just came from a 'bridge' (橋, hashi).
• 0:34 - The 'F' monument. Some have interpreted this to mean 'falling' or 'flying'.
• 0:38 - The children's flags are not 'red-white'. Instead, it's a 'white-black' flag, associated with funerals.
• 0:47 - The so-called 'arrival' (着, ki) time is July 20th at 11:36pm, but it's unusually bright.
• 0:53 - The heart-shaped roof reflects light as well. Some have interpreted this as a broken heart.
• 0:56 - Natsumi looks at the couple (Giko and Shii) with a 'subtle' expression.
• 1:03 - Hattoushin Mona and >>1-san are close friends, which doesn't follow their expected behavior.
• 1:06 - The scene of a railway station at night. Natsumi stands alone on the platform. She notably wears a yellow sundress that we see throughout the animation, rather than the seifuku uniform from earlier.
• 1:08 - The JR train approaches. The clock reads 11:36pm.
• 1:11 - The 'scattering of flower petals' (散華, sange) can be a euphemism for bloodshed or death.
• 1:15 - The buildings are behind the clouds, not on the ground.
• 1:23 - Mona appears in front of a scythe, suggesting that he has the role of the Grim Reaper, which are Shinigami in Japanese culture, or Charon the Ferryman.
• 1:29 -
  • The signposts use 'goroawase', from 'TEN59(Tengoku)' (天国, lit. “Heaven”) to 'Gi59(Jigoku)' (地獄, lit. “Hell”).
  • The children say farewell. Some have speculated that they're stuck in 'Sai no Kawara' (賽の河原), often translated as 'Children's Limbo', and can't be sorted into Heaven or Hell.
• 1:50 - The gate's doors are sickle-themed, with a statue imitating The Thinker over it. The Thinker was originally a segment of The Gates of Hell, which itself is inspired by Dante's Inferno.
• 1:55 - The camera pans to a black sun.

In an interview, the author reveals that Natsumi STEP! was originally about 'recovering from a break-up', but this was changed up since it sounded 'kinda boring',⁶⁾ and we also got this brief bonus animation where Natsumi seems to cry before ominously wielding a crowbar.⁷⁾ With these clues, we're left to presume that she murdered the boy with a crowbar, therefore she was sent to Hell for it.