It is November in Seikyou Academy, and Yuuko and Teiichi investigate the sixth of the Seven Mysteries of Seikyou Academy: "The Interdimensional 13 Steps". After counting many of the staircases around the school, Yuuko decides to take a rest... and Teiichi once again becomes the target of Yuuko's playful attitude.
Soon, the two are accompanied by Kirie, and after listening to how the sixth mystery goes, decides to help out, although she can't help but be surprised that Yuuko does not have an idea on what the mystery suggests. Kirie then adds that there is a much bigger curse awaiting those who solve the first six mysteries, much to the surprise of the two.
Before their conversation goes even deeper, the three are joined by Momoe and a fellow member of the Third Newspaper Club: Sousuke Mihara, a first-year student.
After introducing himself, he goes straight to the point and asks Teiichi, whom he knows can speak to ghosts:
"Do you think it's possible to date a ghost?"
The question takes them to the Old School Building, more specifically the window of the last classroom at the third floor. According to Mihara, he has seen a pair of legs on the same window, but when he tries to look for the person who owns those legs, he comes up empty; it has then aroused his interest to know more about the girl who has eluded him.
And it came to a point where he was desperate. Thus his personal request for Teiichi to handle the case.
Teiichi, although startled at first, decides to help out. With Kirie backing out, the rest continue into the building where the legs are supposed to appear at sunset. They soon reach the end of the building, and Teiichi enters the room where the girl should be sitting when she appears; they found no one there, but Teiichi feels somewhat strange, feeling as if the place does not fit.
Disappointment can be clearly seen in Mihara's face, but he manages to greet the others as they decide to go home for the day. However, Mihara tells Teiichi that he will not give up in knowing the truth behind the "Bare Legs in the Twilight", before he finally leaves.
For some reason, Yuuko is reminded of Teiichi's attitude upon seeing Mihara's determination.
Yuuko then decides to test something.
As Teiichi watches, Yuuko sits by the window of the floor above the Paranormal Investigation Club and tries to reenact what Mihara experienced. (Unknown to Teiichi, Yuuko wants to flaunt her legs to Teiichi, and is hoping for a positive response.)
Soon, Kirie arrives and checks out what they are doing, before handing out her contributions to the investigation, with the school's floor plan marked with stair step numbers. Kirie thinks the based on what she found out, the "Interdimensional 13 Steps" might be hidden from plain view, something that would make the investigation more challenging.
Kirie then notices that it is already sunset, and she suggests that Teiichi should check out the spot once again. At that moment, Teiichi realizes something, and he immediately follows Kirie's suggestion.
When he returns to the place where the sightings happen, Teiichi sees Mihara as he sees the "Bare Legs in the Twilight", and Teiichi gets a first-hand experience of the sighting. Soon, Teiichi asks Mihara to come with him at the place they explored earlier. On their way, Teiichi explains what he discovered: that they might be looking at the wrong place, as the pair of legs are basked in the evening sun while the classroom they visited earlier was blocked from the sun.
There, they discover that there might be a hidden room nearby, and Yuuko discovers it before telling its location to Teiichi: in a lonely locker at the end of the hallway.
Mihara prepares himself as he enters the hidden room, and as Teiichi follows...
...they see a girl in pigtails on the window on the other side of the room.
Who is she?
(in order of appearance)
- The story of "Botan Dorou" is referenced by Momoe on the topic of falling in love with a ghost.